TX 



fiiiiiiiiiiliilii- 



N ELEMENTARY COURSE 
OF 
FOOD CHEMISTRY 



Z. p. EGDAHL 




Class 7^/B'b / 



Copyright N^. 



COPYRIGHT DEPOSIT. 



AN ELEMENTARY COURSE OF 
FOOD CHEMISTRY 

BY 

ZELLA P. EGDAHL, B. S., M. S. 






Copyright, 1913, by 
Z. P. Egdahl. 



Dunn Co. News Co., Menomonie. Wis 



©CLA34-352G 



PREFACE 



In the preparation of this manual the aim has been 
to organize a practical course of food chemistry for 
secondary schools, and, also, to include in one book ma- 
terial from widely different sources. The exercise«s have 
been selected from books of organic, physiological, in- 
dustrial, and sanitary chemistry, with the modifications 
necessary for secondary school work. 

The course requires an elementary knowledge of 
general chemistry. It is intended primarily for students 
of domestic science who desire a knowledge of food 
chemistry applicable to the chemical problems involved 
in cookery and household science. 

It is advisable to use the simplest possible apparatus 
in the experimental work. Much needless waste of time 
can be saved by the elimination of complex apparatus. 
Most of the exercises can be completed in an ordinary 
laboratory period of an hour and a half. 

Since organic chemistry is not a prerequisite of the 
course it is necessary to introduce some preliminary work 
in this subject before proceeding with the chemistry of 
the food-stuffs. A few experiments on the hydrocarbons 
and their derivatives precede the study of the fats, 
carbohydrates, and proteins. The subject matter is ar- 
ranged in accordance with the presentation in most 
books of organic chemistry. Special reference reading in 
Perkin and Kipping 's Organic Chemistry, (London, 
1907) and in Noyes' Organic Chemistry, (N. Y., 1903) is 
indicated at the beginning of each experiment. Any text 
book of organic chemistry may be used in connection 
with class room instruction. In the bibliography the 



books which are of most importance for general refer- 
ence are marked with an asterisk. 

I wish to acknowledge my indebtness to Mr. T. 
R. Moyle, of Stout Institute, for many valuable sugges- 
tions and also for help in the reading of the proof. 

Zella P. Egdahl. 

Menomonie, Wisconsin, January, 1913. 



CONTENTS 

Chapter Page 

I. Composition of organic substances 7 

II. Hydrocarbons. Methane. Acetylene. Illnmina- 
ting gas. Benzene. Fractional distil- 
lation - 10 

III. Alcohols. Ethyl alcohol 22 

IV. Ethers. Ethyl ether 26 

V. Aldehydes and ketones. Formaldehyde. Ace- 
tone 27 

VI. Acids. Acetic acid 31 

VII. Esters. Ethyl acetate. Ethyl butyrate 34 

VIII. Fats 36 

IX. Soaps and glycerine 39 

X. Simple sugars. Glucose. Fructose. Deter- 
mination of reducing sugar in syrup 42 

XI. Disaccharide sugars. Cane sugar. Malt 

sugar.. Milk .sugar 50 

XII. Starches. Starch. Glycogen 55 

XIII. Pectin 60 

XIV. Cellulose 62 

XV. Proteins. Te«ts for nutrients in foods 64 

XVI. Baking powders 73 

XVII. Food adulterants 77 

Bibliography 86 



CHAPTER I 

Composition of Organic Substances 

Organic chemistry has developed from the study of 
products obtained from plant and animal substances. At 
the close of the 18th century Lavoisier, a French chemist, 
demonstrated that, when the organic products of vege- 
table and animal organisms are burned, carbon dioxide 
and water are always formed. Lavoisier showed also 
that the component elements of these bodies are general- 
ly carbon, hydrogen, and oxygen, and frequently nitro- 
gen. It was believed for a long time that organic sub- 
stances could not be formed synthetically from the ele- 
ments, but could be formed only as a result of vital pro- 
cesses. This conception was disproved by Woehler who 
succeeded in preparing urea from ammonium cyanate 
in 1828. Since then most of the organic compounds 
have been artificially prepared. Organic compounds all 
contain carbon so that organic chemistry is now defined 
as the study of the compounds of carbon. Carbon forms 
an exceedingly large number of compounds, over 60,000 
in all, so that a study of these must necessarily be made 
a separate branch of chemistry. The simplest compounds 
of carbon are the compounds of carbon with hydrogen, 
called hydrocarbons. Besides these we have compounds 
of carbon, hydrogen and oxygen, and many which con- 
tain nitrogen m addition. Sulphur and phosphorus also 
enter into the composition of many organic compounds. 
It is possible to introduce, artificially, almost all of the 
elements, both metals and non-metals, as constituents of 
carbon compounds. The number of known carbon com- 
pounds is therefore very great. 



8 ORGANIC COMPOTOJDS 

Experiment No. 1. — Composition of Organic Compounds 

Beading— P. & K., p. 3. 
N., pp. 1-4. 

Apparatus. — 4 test-tubes, beaker (lOOcc), crucible, ring- 
stand, burner. 

Material. — Cane sugar, egg yolk, soda-lime, sodium 
carbonate, potassium nitrate, concentrated nitric 
acid, ammonium molybdate solution, barium chloride 
solution. 

Tests. * 

1. — Place two grams of sugar in a test-tube and heat 
until vapors are given off. Notice the formation of 
moisture on the sides of the test-tube. Test the inflamma- 
bility of the vapors by holding a flame to the mouth of 
the test-tube. Continue the heating until vapors are no 
longer evolved. What is left in the test-tube? Break 
the tube and examine the residue. Sugar is composed of 
which elements? 

2. — Allow half of an egg yolk to dry between filter 
paper, or, better, dry on a watch glass in the warming 
oven. Mix a small amount of the dry egg yollv with an 
excess of soda-lime, transfer to a test-tube and heat. Test 
the reaction of the vapors to moist litmus paper. Do the 
fumes smell of ammonia gas? Hold a rod moistened in 
hydrochloric acid to the mouth of the test-tube. What 
occurs? Do all organic compounds contain nitrogen. 

3. — Prepare a fusion mixture by mixing equal 
amounts of powdered potassium nitrate and sodium 
carbonate. To a piece of the dry egg yolk the size of a 
pea add an equal amount of the fusion mixture and fuse 
in a crucible on a clay triangle over the free flame. When 
mixture is well fused, (the substance melts and then 
solidifies), allow to cool. Divide the fused mass into two 
portions and reserve one portion for 4. Dissolve the other 
portion in 5 cc. of dilute nitric acid, filter, and add 5 cc. 
of ammonium molybdate to the filtrate. The formation of 
a fine yellow precipitate, especially on warming, indi- 
cates the presence of phosphates. By treatment with the 



ORGANIC COMPOUNDS 9 

fusion mixture the phosphorus in the egg yolk has been 
converted into a phosphate compound. 

4. — Dissolve the remainder of the fused mass in 5 cc. 
of dilute hydrochloric acid, filter into a test-tube and add 
a few drops of barium chloride solution. The formation 
of a white precipitate indicates the presence of sulphates. 
The fusion mixture oxidizes the sulphur in the egg yolk 
to a sulphate compound. 

Place a small amount of egg yolk on a bright silver 
coin. Moisten and allow to stand for a few minutes. 
What is the result ? What causes the tarnishing of silver ? 



CHAPTER II 

Hydrocarbons 

Classification of Hydrocarbons — Eiehter, Organic Chem- 
istry, p. 78. 

I. Fatty Bodies: Aliphatic compounds, chain- 
like carboiv compounds, methane series. 

II. Carbocyclic Compounds: Aromatic com- 
pounds, carbon ring compounds, benzene series. 

III. Heterocyclic Compounds: Mixed ring com- 
pounds. 

I. Fatty Bodies. 

A. Saturated Hydrocarbons, Paraffins. 

G n Hg 2 

Lower Members of Paraffin Series With all Known 

Isomerides. 
Paraffin Boiling Point 

1. Methane, CH^ -160° 

2. Ethane, C^He -93° 

3. Propane, CgHg —45° 

4. Butanes, C^Hi^ 

Normal +1° 

Iso-butane — 17° 

5. Pentanes, CgH^g 

Normal 38° 

Dimethyl-ethyl methane 30° 

Tetra-methyl methane 10° 

6. Hexanes, CeH^^ 

Normal hexane 71° 

Methyl-diethyl methane 64° 

Dimethyl-propyl methane 62° 

Di-iso propyl . ; 58° 

Trimethyl-ethyl methane 43°" 



•HYDROCAKBONS 



11 



Higher Members of the Known Normal 

Melting Boiling 
Point Point 



98.4° 
125.5° 
149.5° 
173° 



7. Heptane, 

CyHie 

8. Octane, 

9. Nonane, 
CA„ -51° 

10. Decane, 
C10H22 — 32 

11. Undecane, 
C11H24 —26.5° 194.5° 

12. Dodecane, 
C12H26 —12° 214° 

13. Tridecane, 
CeH^s -6.2° 234° 

14. Tetradecane, 
C14H30 5.5° 252.5° 

15. Pentadecane, 
C15H32 10° 270.5° 

16. Hexadecane, 
CieH34 18° 287.5° 

17. Heptadecane, 
C,,H36 22.5° 303° 

18. Octadecane, 
CJ-I,, 28° 317° 

19. Nonadecane, 
C,,ri4, 02° 330° 

20. Eicosane, 

aoH,, 36.7° 205° (15mm. pr.) 

21. Heneicosane, 

C21H44 40.4° 215° (15mm. pr.) 

22. Docoisane, 

C22H46 44.4° 224.5° (15mm. pr.) 

23. Tricosane, 

asH^s 47.7° 234° (15mm. pr.) 

24. Tetraeosane, 

C2A0 51.5° 243° (15mm. pr.) 



Hydrocarbons 
Sp. Gr. 
0.7006(0°) 
0.7188(0°) 
0.7330(0°) 
0.7456(0°) 
0.7745 (m. p 
0.773 (m. p 
0.775 (m. p 
0.775 (m. p 
0.775 (m. p 
0.775 (m. p 
0.776 (m. p 
0.776 (m. p 
0.777 (m. p 
0.777 (m. p 
0.778 (m. p 
0.778 (m. p 
0.778 (m. p 
0.778 (m. p 



12 HYDROCARBON* 

Melting Boiling 
Point Point Sp. Gr. 

27. Heptaeosane, 
C27H56 59.5° 270° (15mm. pr.) 0.779 (m. p.) 

31. Hentriacontane, 

CsiHe^ 68.1° 302° (15mm. pr.) 0.780 (m. p.) 

32. Dotriacontane, 

C32H66 70° 310° (15mm. pr.) 0.781 (m. p.) 

35. Pentatriacontane, 

O35H72 74.7° 331° (15mm. pr.) 0.781 (m. p.) 

€0. Dimvricyl, • 

CeoH,,, * 162° 

B. Unsaturated Hydrocarbons. 

1. Olefines. 
2. Acetylenes. 

Paraffins 

Physical Properties of the Paraffins. The lower 
members of the paraffins up to butane are gases, the in- 
termediate members are colorless liquids, and the high- 
er members beginning with hexadecane, C-igHg^, are 
solids. The paraffins are insoluble in water, but the low- 
er and intermediate compounds dissolve readily in al- 
cohol and in ether. The solubility decreases with the 
increase in molcular weight. Dimyricyl, C60H122 is quite 
insoluble. It will be seen from the tables that the boil- 
ing point increases with the increase in molecular weight. 

Chemical Properties. The paraffins are chain-like 
compounds. The structural formulae assigned to some of 
the lower members are as follows : 

Methane Ethane Propane ' 

H H H H H H 

I II III 

H— C— H H— C— C— H H— C-C— C— H 

I - I I III 

H H H H H H 



HYDJROCARBONS 13 

Normal butane Isobutane, (trimethyl methane) 

H 

I 
H H H H H H— C— H 

I I I I II 
H— C^C— C— C— H H— C C -H 

I I I I I • I 

H H.H H H H— C--H 

I 
H 

The paraffins form a homologous series of hydrocar- 
bons. Each member differs from the preceeding mem- 
ber by a constant difference of CH2. Beginning with 
butane they occur in isomeric forms. Isomers are com- 
pounds which have the same molecular formula but 
which differ in constiti^tion. Compare the structural 
formulae of butane and isobutane. 

The paraffins are very stable, saturated compounds. 
When heated they burn forming carbon dioxide and wa- 
ter. The chief reactions of the paraffins are substitu- 
tion reactions. It is possible by chemical methods to 
substitute for the hydrogen atoms in the compounds oth- 
er univalent elements or groups. One or more of the hy- 
drogen atoms may be so substituted. It is possible to re- 
place the hydrogen by a halogen, a hydroxyl group, an 
amido group, a nitro group and so forth. The most im- 
portant substitution products of the paraffins are the 
mono-substitution products, i. e., the compounds in which 
one hydrogen has been replaced. These mono-substitu- 
tion products are called alkyl compounds. The hydro- 
carbon radical in these compounds is called the alkyl 
radical and is represented by R in the general formulae 
of the compounds. 



14 


HYDROCARBONS 

• 


Paraffin | Alkyl radical | Alkyl chloride 


CnH2n+2 1 


C„H.n-l (R) 1 RCI 


Ethane 


Ethyl radical 


Ethyl chloride 


C,He 


C.H, 


C,H,C1 


Propane 


Propyl radical 


Propyl chloride 


CaH^ 


C3H, 


CgH^Cl 


Below is a list of the chief derivatives of the para- 


ffins: 


Alcohols, ROH 


Ethers, ROR 


Aldehydes, RCHO 


Ketones, RCOR 


Acids, RCOOH 


Esters, RCOOR 


The relation between some of these compounds may 


ioe seen by the following table: 


Paraffin | Alcohol | Aldehyde | Acid 



methane 



ethane 



CgHe 



propane 



CgHj 



methyl 
alcohol 
CH3OH 

ethyl 
alcohol 



OH 



propyl 
alcohol 

CgH.OH 



formalde- 
hyde 
HCHO 

acet- 

aldehyde 

CH3CHO 

prop- 
aldehyde 
CsH.CHO 



formic 
acid 
HCOOH 

acetic 

acid 

CH3COOH 

propionic 

acid 

C2H5COOH' 



. Methane. Methane, CH4, or marsh gas, is the first 
member of the paraffin series of hydrocarbons.^ It is 
formed by the decay of vegetable matter and is liberated 
in swamps and in mines. When mixed with air methane 
forms an explosive mixture, the deadly fire-damp of coal 
mines. Methane with other gaseous hydrocarbons occurs 
in natural gas and in illuminating gas. American petro- 
leum is rich in the paraffin hydrocarbons. Methane may 
be obtained from petroleum by fractional distillation but 



HYDROCARBONS 15 

it is very difficult to isolate it completely from the other 
hydrocarbons. In the laboratory methane is made by 
heating a mixture of sodium acetate and soda lime. The 
reaction is between the acetate and the sodium hy- 
droxide. The lime is used to prevent corrosion of the 
glass vessel through the action of the molten sodium hy- 
droxide. 

CHgCOONa+NaOH-^Na.COs+CH, 

Experiment No. 2. — Methane. 
Reading— P. & K. p. 53. 

N. p. 58. 
Apparatus. Round bottom flask (250cc.), cork, delivery 
tube, iron stand fitted with iron ring and clamp, 4 
small wide mouth bottles (6 oz.), dish of water, Bun- 
sen burner, wire gauze. 
Material. Dehydrated sodium acetate, sodium hy- 
droxide, quick lime. 
Preparation. Fit a round bottom flask with cork and de- 
livery tube ; thoroughly mix lOg of dehydrated 
sodium acetate, lOg. of powdered sodium hydroxide, 
and 15g. of quick-lime and add to flask. Heat flask 
carefully but .strongly over a wire gauze. Collect 
three bottles of the gas by displacement of water. 
Tests. 

1. — Apply a lighted splint to the gas in the first bot- 
tle. Describe the flame. 

2.^Invert a bottle of air over the second bottle of 
gas. In a few seconds test both bottles with a lighted 
splint. Is methane lighter or heavier than air? 
3.— Has methane any color or odor? 

Acetylene. Acetylene, CgHg, is an unsaturated hy- 
drocarbon. It can be prepared directly from its elements. 
When an electric spark is passed between carbon points 
in an atmosphere of hydrogen, acetylene is formed. 

Acetylene is made commercially by the action of wa- 
ter upon calcium carbide. 

CaC2+2H20^Ca ( OH) 2+C2H2 



16 HYDROCARBONS 

Acetylene when pure has a pleasant, ethereal odor 
and can be liquified at -|-1° under a pressure of 48 at- 
mospheres. Acetylene burns with a smoky flame and 
when mixed with air forms an explosive mixture. Spec- 
ially constructed burners have been devised in which 
acetylene can be burned without smoking. Under these 
conditions the acetylene flame is very brilliant. 

Acetylene like the other members of the unsaturated 
hydrocarbons is very active. It combines directly with 
the halogens forming ethylene and ethane halides. It also 
anites with hydrogen forming ethylene and ethane. 
Acetylene reacj^s with the metals to form metallic acety- 
lides some of which are very explosive. For this reason 
it is unsafe to store acetylene gas in metallic holders. 
Acetylene polymerizes at red heat and forms benzene. 
Three molecules unite to form one molecule of benzene. 

0O2H2 — ^^elle 

Experiment No. 3. — Acetylene 

Reading— P. & K. p. 81. 

N. p. 87. 
Apparatus. 3 wide mouth bottles, basin of water. 
Material. Calcium carbide, bromine water. 
Preparation. Drop a small lump of calcium carbide into 

a basin of water and collect three bottles of the gas 

by displacement of water. 
Tests. 

1. — Describe the physical properties of the gas. 

2. — Apply a lighted splint to the gas in one of the 
bottles. Describe the flame. 

3. — Add a few drops of bromine water to the third 
bottle of gas. What is formed? Notice the odor. 

Illuminating Gas. When bituminous coal is heated 
to a high temperature in the absence of air it is decom- 
posed into a number of products one of which is illum- 
inating gas. The process is known as destructive dis- 



HYDROCARBONS 17 

tillation. The diagram illustrates the products obtained 
by the destructive distillation of Newcastle coal. 

COAL 



I I II 

COAT; GAS GAS LIQUOR COAL TAR COKE 



LIGHT OILS HEAVY OILS PITCH 



benzene, toluene, xylene, carbolic acid, anthracene, 
naptha, carbolic acid, pyrene, cresylic acid, acri- 

pyridine, etc. dine, uapthalene, phenan- 

threne, etc. 

Illuminating gas is a mixture of methane, some of 
the heavier hydrocarbons, carbonic oxide, hydroyen, 
oxygen, and carbon dioxide. 

Experiment No. 4. — Illuminating gas 

Apparatus. Hard glass test-tube, one hole stopper, de- 
livery tube, pan, wide mouth bottle, clamp, ring- 
stand, burner. 

Material. Soft coal. 

Preparation. Fill a hard glass test-tube one third full of 
soft coal, fit with a cork and delivery tube; clamp 
the test-tube in a horizontal position and heat, gent- 
ly at first, and then quite strongly. Collect gas by 
displacement of water. 

Tests. 

1. — What are the physical properties of the gas? Is 

the gas pure? 

2. — Hold a lighted splint to the mouth of a bottle of 

the gas. 

3. — Collect a bottle of gas from the gas jet and com- 
pare with the coal gas which you have prepared. 



18 HYDROCARBON^ 

Benzene. Benzene is the first member of the car- 
bocyelic or ring compounds. Carbocyelic means that car- 
bon atoms alone form the ring. When some other ele- 
ment besides carbon enters into the ring the compound is 
designated as heterocyclic. The structural formula which 
Kekule has assigned to benzene is given below: 

HC CH 

II . I 

HC CH 

\ / 
CR 

Other formulae have been proposed but in every case 
the ring formation is represented. The cyclic compounds 
are compounds in which the carbon atoms are 
joined to each other in such a way as to form a ring of 
carbons. It can easily be seen that these compounds dif- 
fer quite materially from the aliphatic or open chain 
compounds. The benzene hydrocarbons are sometimes 
called the aromatic hydrocarbons. 

Benzene is obtained from coal tar by distillation. A 
number of other hydrocarbons of this series are obtained 
in the same way. The principal compounds are named in 
the table below; 

Benzene series of hydrocarbons, C nHg" q 

Benzene CJIq 

Toluene C^H^ 

Xylene CgHio 

Mesitylene p ^ 

Pseudocumene C9M12 

Durene p tt 

Cymene CioHi* 

Hexa-methyl benzene CigHig 

In the laboratory benzene is made by heating benzoic 
acid or calcium benzoate with soda-lime. Benzene is 



HYDROCARBONS 19 

manufactured on a large scale for use in the preparation 

of the dye-stuffs. 

Experiment No. 5. — Benzene. Nitro-benzene 

Beading— P. & K. p. 305. 
N. p. 93 p. 107. 

Apparatus. Large test-tube, stopper, delivery tube, 
ring-stand, clamp, condenser tube, Bunsen burner. 

Material. Benzoic acid, quick lime, cone, nitric acid, 
cone, sulphuric acid. 

Preparation. Mix 8 grams of benzoic acid with an equal 
weight of quick lime and place in a large, dry test- 
tube fitted with a one hole stopper. Clamp the test- 
tube in a horizontal position and connect with a dry 
condenser tube. Heat the test-tube gently at first 
and then quite strongly. Continue heating until sev- 
eral cc. of distillate collect in the receiver. 
CeH,COOH-fCaO-^CeHe+CaC03 

Tests. 

1. — What are the physical properties of benzene? 

2. — Pour a few drops of the distillate into a small 
evaporating dish of water. Is the distillate heavier or 
lighter than water. Apply a lighted splint to the surface 
of the water. 

3. Nitrobenzene. — Mix 2 cc. of concentrated nitric 
acid with the same amount of concentrated sulphuric 
acid in a test-tube and add gradually the remainder of 
the distillate, keeping the mixture at a temperature un- 
der 50° ; allow the mixture to stand for a few minutes 
and then pour into a beaker of water. The nitrobenzene 
separates out as a heavy yellow oil which has the odor of 
almonds. 

Experiment No. 6. — Fractional Distillation of Benzole 

Reading— P. & K. pp. 10-12. 

N. p. 13. 
Apparatus. Distilling flask, condenser and condenser 



20 HYDROCARBOJ^S 

clamps, ring-stand, thermometer, 6 Erienmeyer 
flasks (lOOce.), wire gauze, burner. 

Material. Commercial benzole, ("90 percent benzole.") 

Distillation of Benzole. Commercial benzole con- 
sists of a mixture of about 70 per cent benzene and 24 per 
cent tolulene with some other impurities. The boiling 
point of. benzene is 81°, and of toulene 111°. Benzole 
being a mixture will boil at some temperature lying be- 
tween the boiling points of its constituents. It is possible 
by fractional disitillation to separate the mixture into 
its constituents. 

Place lOOcc. of benzole in a distilling flask fitted with, 
stopper and thermometer the bulb of which is level with 
the side tube of the flask. Connect the flask with the 
distilling apparatus. Have ready 6 small dry flasks in 
which to collect the different portions of the distillate. 
Label the flasks as follows: No. 1. Under 80°, No. 2. 80- 
85°, No. 3. 85-90°, No. 4. 90-95°, No. 5. 95-100°, No. 6. 
Over 100°. 

Carefully heat the benzole and when it begins to 
boil, collect in flask No. I. the fraction which comes over 
under 80°, then change the receiver and collect in the 
second flask the fraction which distills over between 80 
and 85°. Continue the distillation until all six fractions 
have been collected. Measure the amount of each frac- 
tional distillate and record the amounts in your note 
book. "When the temperature reaches 110°, cease the 
distillation. Pour the residue in the distilling flask into 
another vessel; add the first fraction, i. e., that which dis- 
tilled over under 80°. to the distilling flask and again col- 
lect the fraction under 80° in flask No. I. As soon as the 
temperature reaches 80°, remove flame and add the sec- 
ond fraction to the distilling flask. Again distill, collec- 
ting the distillate which comes over under 80° in flask 
No. 1., and that which comes over between 80° and 85° in 
flask No. 2. As soon as the temperature reaches 85°, re- 
move the flame and add the third fraction. In the same 
way add the fourth fraction at 90°, the fifth at 95°, and 



HYDROCARBONS 21 

SO on until all the six fractions have been refractionated 
Again measure the fractional distillates. Redistill all 
the fractions again. This time it will be seen that there 
is a definite separation of the distillate into two liquids, 
one having a boiling point around 82°, and the other 
boiling near 110°. Measure the amount of your final 
fractions. 



CHAPTER III. 
Alcohols 

Monohydric Alcohols. The monohydric alcohols 
are alcohols containing one hydroxyl group. They 
are represented by the general formula ROH in 
which R stands for the hydrocarbon radical. They may 
be regarded as derivatives of the hydrocarbons in which 
one hydrogen has iSeen replaced by the hydroxyl group. 

Methane— CH4, Methyl alcohol— CH3OH. 

Ethane-C^He, Ethyl alcohol— C^H^OH. 

Propane — CgHg, Propyl alcohol — C3H7OH. 
Only one methyl and one ethyl alcohol are known. 
There are two isomeric propyl alcohols, four butyl alco- 
hols and, of the higher alcohols, many isomerides can be 
obtained. The difference between the isomeric alcohols 
is illustrated by the structural formulae of the propyl 
and butyl alcohols. 

Propyl alcohol Isopropyl alcohol 

CH3.CH2.CH2.OH CH3.CH(0H).CH3 

Primary Secondary Primary 

butyl alcohol butyl alcohol isobutyl alcohol 



CH3 




CH3 


CH3 


1 

CH. 




CH2 


CH3-CH 


1 
CH2 




CH.OH 

1 


CH,OH 


CH2.OH 




CH3 




Tertiary isobutyl alcohol 
CH3 






CH3- 


-C— OH 

1 
CH, 







ALCOHOLS 23 

Alcohols which have the formula R — CHg OH are 
classed as primary alcohols. Secondary alcohols corres- 
pond to the general formula RgCHOH. Tertiary 
alcohols have the formula R3COH. A primary 
alcohol on oxidation yields an aldehyde, and on fur- 
ther oxidation an acid is formed. The acid contains as 
many carbon atoms as the alcohol from which 
it is derived. Secondary alcohols on oxidation yield 
ketones. On oxidation ketones yield acids of less 
number of carbon atoms than the parent molecule. Ter- 
tiary alcohols break down on oxidation into simpler com- 
pounds. The oxidation products of the alcohols are very 
important since they serve to indicate the nature of the 
alcohol, that is, whether the alcohol is a primary, secon- 
dary, or tertiary compound. 
Primary 
alcohol Aldehyde 

R-CH^OH+O^R-CHO+H^O 

Aldehyde Acid 

R -CHO+0->R— COOH 
Secondary 

alcohol Ketone 

R.CHOH+O-^R^CO+H.O 

Polyhydric Alcohols. Polyhydric alcohols are alco- 
hols containing two or more hydroxyl groups. Glycer- 
ine, the alcohol obtained from fats, is one of the most im- 
portant of the polyhydric alcohols. Glycerine is a trihy- 
dric alcohol and has the formula C3H5(0H)3. 

^ Ethyl Alcohol, C.H.OH. Ethyl alcohol, (grain al- 
cohol), and methyl alcohol, (wood alcohol), are the 
alcohols most commonly used. Methyl alcohol is 
prepared from the products of the destructive 
distillation of wood. Ethyl alcohol is prepared commer- 
cially by the fermentation of solutions containing sugar. 
The sugar solutions are obtained from the molasses left 
after the removal of crystallizable sugars, or from solu- 
tions prepared from starchy substances. The latter pro- 
ducts are generally made from corn or potatoes. 



24 ALCOHOLS 

• 

The fermentation of the sugar is caused by chemical fer- 
ments, or enzymes, secreted by yeast. The action 
of enzymes is not definitely known. They are 
supposed to act as catalytic agents. Yeast causes 
the fermentation of solutions of cane sugar as well 
as solutions of simpler sugars, i. e. glucose. If cane sug- 
ar is used it is first converted into simpler sugars through 
the action of an enzyme in yeast called invertase. The 
simple sugars are then decomposed into alcohol and car- 
bon dioxide through the action of another enzyme, 
zymase. * 

Cane sugar invertase glucose fructose 

zymase Alcohol carbon dioxide 
CfiHi^Oe > 2C2H,OH + 2C0o 

Experiment No. 7. — Alcohol 

Reading— P. & K. pp. 89-103. 
N. pp. 124-134 

Apparatus. Flask (500cc.), stopper, delivery tube, wide 
mouth bottle, condenser, Erlenmeyer flasks (75ec), 
evaporating dish, test-tube, thermometer. 

Material. Molasses, compressed yeast cake, lime water, 
kerosene, iodine crystals, potassium carbonate solu- 
tion. 

Preparation. In a 500cc. flask place 200cc. of water and 
25cc. of molasses. Mix well and add i/4 of a cake of 
compressed yeast which has previously been mixed 
with a little luke warm water (i. e. water at 37°). 
Stopper flask with a stopper fitted with a delivery 
tube which dips beneath the surface of some lime 
water in a wide mouth bottle. This bottle should 
not be stoppered, but the surface of the lime water 
should be covered with a layer of kerosene to ex- 
clude the air. Set the apparatus in a warm place 
for 24 hours. At the end of that time, if fermenta- 



ALCOHOLS 25 

tion has been vigorous, (this can be judged by the 
cloudiness of the lime water), strain the contents of 
the flask through muslin. Place the strained liquid 
in a distilling flask fitted with a thermometer and 
connect with condenser. Heat the flask carefully 
until the liquid boils; then regulate the heat so as 
to keep the liquid boiling gently. Distill about 50cc. 
of distillate. Place distillate in a clean, dry distill- 
ing flask, fitted with thermometer, add a few lumps 
of quick lime and re-distill. Watch the temperature 
and cease the distillation as soon as the temperature 
rises above 90°. A few cc. of impure alcohol are ob- 
tained by this method. 

Tests. 

1. — Place 2cc. of the alcohol in an evaporating dish 
and ignite. 

2. — Place Ice. of the alcohol in a test-tube, add a 
small crystal of iodine and then add Ice. of potassium 
carbonate solution. Warm gently and observe odor and 
precipitate. Alcohol is converted into iodoform by this 
method, and, if enough alcohol is present, a yellow pre- 
cipitate of iodoform will separate out. Even with traces 
of alcohol, however, the odor of iodoform is quite dis- 
tinct. 

Questions. 

1. — What was the milky precipitate in the flask of 
lime water? 

2. — How is alcohol prepared commercially? 

3. — How can alcohol be separated from water? 



CHAPTER IV 

Ethers 

Ethers are alkyl derivatives of the alcohols. They 
have the general formula ROR. 

Methyl Ether. Methyl ether, CH3OCH3, is prepared 
by heating methyl alcohol vs^ith sulphuric acid. It is a 
gas having a pleas^t, ethereal odor. It can be liquified 
at -23°. 

Ethyl Ether. Ethyl ether or ether, C2H5OC2H5, is 
the most important of the ethers. It has been knov^n for 
a \ery long time. It was described in the 16th century 
by a German physician. Ether is prepared from ethyl 
alcohol and sulphuric acid. It is a pleasant-smelling 
colorless liquid boiling at 35°. It is volatile and highly 
inflammable. Ether is used as a solvent and as an anes- 
thetic. 

Experiment No. 8 — Ether 

Reading— P. & K. pp. 111-118. 

X. pp. 164-168. 
Apparatus. Test-tube, Bunsen burner. 
Material. Concentrated sulphuric acid, alcohol. 
Test. 

Carefully add 5cc. of cone, sulphuric acid to a test- 
tube containing 5cc. of alcohol. Warm gently until the 
liquid appears to boil. Determine the odor of tlie product 
in the test-tube. Ether is formed by the interaction of 
the alcohol and acid. Ethyl hydrogen sulphate is first 
formed and this reacts with more alcohol to form ether. 
The process is continuous. 

C^H^OH-fH^SO.^C^H^HSO^-fH^O 
C^H.HSO.-j-CaH.OH^CsH^OC^Hs-f-H^SO, 



CHAPTER V 

Aldehydes and Ketones 

Aldehydes. The aldehydes are intermediate pro- 
ducts formed by the oxidation of primary alcohols. When 
the alcohols are completely oxidized acids are formed. 
It is possible, however, by proper precautions, to obtain 
products intermediate between the alcohols and acids. 
These products are called aldehydes, from alcohol dehy- 
drogenatum, since they may be regarded as alcohols 
from which hydrogen has been removed. 

Formaldehyde. Formaldehyde is the aldehyde most 
commonly used. It is probably the first product formed 
in the synthesis of carbohydrates in vegetable cells. It 
is prepared by passing vaporized methyl alcohol, mixed 
with air, over heated platinised asbestos. CH3. 0H-|-0 
^H. CH0+II20. Special lamps have been constructed 
for the production of the gas. Formaldehyde is a gas at 
ordinary temperatures. It can easily be condensed to a 
liquid having a boiling point of —21°. Formaldehyde 
dissolves readily in water. Formalin is a commercial 
solution of formaldehyde containing about 40 per cent 
of the gas. An aqueous solution of formalin reduces 
metallic hydroxides, forming metallic oxides. With am- 
moniacal silver nitrate solution, metallic silver is formed. 
Formaldehyde has a destructive influence on the lower 
forms of life, i. e. bacteria and molds, and is much used 
as a disinfectant. 

Ketones. The ketones are formed by the oxidation 
of secondarv alcohols. They have the general formula 
R2CO. 

Acetone CHo. CO. CH3 is the best known of the ke- 
tones. It is obtained from crude wood spirits, one of the 
products of the destructive distillation of wood. Techni- 
cally it is prepared by the distillation of calcium acetate. 



28 



ALDEHYDES AND KETONES 



Acetone shows the general properties of the ketones. It 
is used as a solvent and in the manufacture of sulphonal, 
chloroform and iodoform. 

A knowledge of the general properties of aldehydes 
and ketones is very important in food chemistry since 
the simple sugars are either aldehyde or ketone deriva- 
tives and therefore show many of the properties of these 
bodies. In the tables below a list of the more important 
properties of the aldehydes and ketones is given. 



Reagent 



Reducing agents 
(sodium amalgam 
and water, Zn and 
HCl) 



Oxidizing agents 



Aldehydes 



form primary alco- 
hols 



form acids of same 
number of carbon 
atoms. 



Fehjling's solution reduced by aldehy- 
des 



Amm. silver nitrate 



reduced by aldehy- 
des 



Phenylhydrazine form hydrazones 



Ketones 



form secondary al- 
cohols 



form acids each 
containing less no. 
of carbon atoms 



not reduced by ke- 
tones 



not reduced by ke- 
tones 



form hydrazones 



Experiment No. 9. — Formaldehyde 

Reading— P. & K. pp. 118-122. 
N. pp. 170 176. 

Apparatus. — 4 test-tubes, beaker, 2 watch glasses, plat- 
inum wire. 

Material. — Formalin, ammonical silver nitrate, Fehling's 
solution, milk, cotton wool, lime water, phenol- 
phthalein solution, methyl alcohol. 



ALDEHYDES AND KETONES 29 

Preparation. Prepare some formaldehyde as follows: 
Place 10 ec. of methyl alcohol in a small beaker; 
heat a spiral of platinum wire to dull redness in a 
flame and quickly suspend the heated wire over the 
alcohol. Notice the odor of the vapors which are 
evolved. Generally a slight explosion occurs. 

Tests. Use Formalin, for these tests. 

1.— Add a few drops of formalin to 5 cc. of water in 
a test-tube ; pour in a few drops of an ammoniacal solu- 
tion of silver nitrate and warm gently. The formation of 
a silver mirror on the bottom of the test-tube shows the 
reducing property of the aldehyde. 

2. — Add a drop of formalin to 5 cc. of Fehling's 
solution ^ in a test-tube, and heat to boiling. The 
brick red precipitate, (cuprous oxide), is formed as a 
result of the action of the aldehyde on the copper 
hydroxide. Fehling's solution is an alkaline tartrate 
solution of copper hydroxide. The aldehyde reduces the 
copper hydroxide to cuprous oxide. 

3. — Fill two test-tubes two-thirds full of fresh milk 
and label the tubes A and B. To A add a few drops of 
formalin and mix well. Plug both tubes with cotton wool 
and allow to stand for 24 hours at room temperature ; 
then examine each tube and note odor, coagulation and 
acidity. Make the acidity test as follows: Add enough 
lime water to 10 cc. of phenolphthalein solution to pro- 
duce a faint pink color ; pour 5 cc. into each of two watch 
glasses. To one w^atch glass add the milk from A, and to 



* Note. Fehling's solution is an alkaline tartrate 
solution of copper hydroxide. It is made up in two parts, 
A, and B: B is a solution of potassium or sodium 
hydroxide and Rochelle salts (sodium potassium tar- 
trate) and A is a solution of copper sulphate. For use 
equal parts of A and B are mixed. 



30 ALDEHYDES AND KES'ONES 

the other add the milk from B. Add the milk carefully, 
a few drops at a time, and see if, in either ease, the 
phenolphthalein solution is decolorized. Unless too much 
lime water has been added to the phenolphthalein solution, 
this test will serve to show the presence of a slight 
amount of acid in the milk. Can you tell which test-tube 
contains the most acid"? Why is formaldehyde con- 
sidered a good disinfectant? 

Experiment No. 10 — Acetone 

Eeading— P. & K. pp. 130-145. 

N. p. 187. 

Apparatus. Hard glass test-tube, clamp, distilling appar- 
atus, 2 test-tubes, Bunsen burner. 

Material. Barium acetate, ammoniacal silver nitrate, 
Fehling's solution. 

Prepration. Place 15g. of powdered barium acetate in 
a large hard glass test-tube and connect with a con- 
denser. Clamp the test-tube in a horizontal posi- 
tion. Heat the test-tube containing the acetate 
strongly but evenly. When two or three cc. of dis- 
tillate have been obtained stop the distillation. The 
distillate contains acetone mixed with water and 
other impurities. Use distillate for the tests. 

Barium Barium 

acetate carbonate Acetone 



CH,COO 



CH.COO 



Ba -^ BaCOg+CHgCOCHg 



Tests. 

1. — What are the physical properties of acetone? 

2. — Use a few drops of the distillate and make 
tests 1 and 2 given under aldehyde. 



CHAPTER VI 
Acids 

Fatty Acids. The acids derived from the paraffins 
are called fatty acids because many of the acids which 
enter into the composition of the fats belong to this ser- 
ies. Fatty acids are formed by the complete oxidation 
of primary alcohols. The relation between the paraffin, 
alcohol and acid is shown in the table given in chapter 
II. The most important fatty acids are given below. 

Formic— HCOOH 
Acetic— CH3COOH 
Propionic-C^H^COOH 
Butyric- C3H7COOH 
Caproic— C^H.^COOH 
Caprylic— CVH,,COOH 
Capric— CgH.gCOOH 
Laurie— C.iH^sCOOH 
Myristic— C.sH.^COOH 
Palmitic— Ci^Hg.COOH 
Stearic— C17H35COOH 

The first member of the series, formic acid, is formed 
by the oxidation of methyl alcohol. Acetic acid, the acid 
in vinegar, is formed from ethyl alcohol. Propionic acid 
is likewise prepared from its corresponding alcohol. 
Butyric acid is practically prepared by the butyric acid 
fermentation of glucose. It can be obtained in small 
amounts from butter fats. Palmitic and stearic acids 
are obtained by the hydrolysis of the fats, especially suet 
and tallow. Oleic acid, C17H33COOH, an unsaturated 
acid, is obtained from these fats and also from lard, olive 
oil, cotton seed oil and other oils. 



32 ACIDS 

Experiment No. 11. — Acetic acid 

Reading— P. & K. pp. 145-156. 

N. p. 220-227. 

Apparatus. Round bottom flask (250cc.), reflux conden- 
ser, sand bath, ringstand, wire gauze, Bunsen burn- 
er, beaker, 2 test tubes. 

Material. Potassium bichromate, cone, sulphuric acid^ 
alcohol, sodium hydroxide, ferric chloride. 

Preparation. Garrptt and Harden-Practical Organic 
Chemistry, p. 39. "Place 30g. of coarsely powdered 
potassium bichromate in a round-bottomed flask, 
and add a cold mixture of 30g. cone, sulphuric acid 
with 18cc. of water; place the flask on a sand 
bath and connect it with a back flow condenser, and 
then add gradually 5c c. of alcohol diluted with an 
equal volume of water. After each addition, a vig- 
orous reaction takes place, and the liquid becomes 
very hot ; allow all action to cease before adding the 
next quantity, but do not cool the flask. When all 
the alcohol has been added, boil for ten minutes, then 
connect the flask with the other end of the condenser 
and distill over wire gauze, until about 20cc. of dis- 
tillate have come over. This consists of aqueous 
acetic acid, but usually also smells slightly of acetic 
ether and aldehyde." Use distillate for the tests. 

Potassium Sulphuric Potassium 

Alcohol bichromate acid bisulphate 

3C2H,OH -f 2K2Cr,0, + lOH^SO^ -> 4KHS0, 

Chromium 

sulphate Acetic acid Water 

+ 2Cr2(SOj3 + 3 C^HA + 11 H,0 

Tests. 

1. — Describe the odor of acetic acid. 

2. — Carefully neutralize a portion of the distillate 
with sodium hydroxide, and then add a few drops of fer- 



ACIDS 33 

ric chloride. The red coloration indicates the presence of 
the acetate. Repeat this test with a few drops of uncol- 
ored vinegar instead of the distillate. 

3. — Take 4cc. of the distillate and add Ice. of alcohol 
and 2cc. of cone, sulphuric acid. Mix well and then de- 
termine the odor. Acetic ether is formed and may be 
recognized by its odor. 

Questions. 

1. — How is vinegar prepared commercially? In 
this case what is the oxidizing agent? 



CHAPTER VII 

Esters 
Esters. Esters are acid derivatives formed by re- 
placing the hydrogen of the carboxyl group of the acid 
by some hydrocarbon radical. If the acid is an organic 
acid the ester will have the general formula RCOOR. 
The esters are named according to the acids from which 
they are derived. The ethyl ester of nitric acid is ethyl 
nitrate, CoH-NOo, of acetic acid, ethyl acetate, CH3COO 
CoH-. The esters are prepared by several different meth- 
ods. A general method for their formation is by the 
condensation between an acid and an alcohol. Sulphuric 
acid is generally used as the condensation agent. 

Fattv acid Alcohol Ester Water 

R("OOH + ROH > RC^OOR + H.O 

When esters are heated with water, dilute acids, and 
alkalies, they are hydrolized with the formation of the 
free acid, or salt of the acid, and the alcohol. This reac- 
tion is spoken of as saponification because it is the reac- 
tion used in soap making. 

Ester Acid Alcohol 

RCOOR+H,O^RCOOH+ROH 

The esters are used in the manufacture of artificial 
fruit flavorings. Etbyl butyrate, C.H.COOC.H,, is used 
for pineapple flavor. Pentyl acetate, CHgCOOC^Hj^, is 
used as pear flavor. Banana essence is made up of pentyl 
acetate and ethyl butyrate, and apple essence is com- 
posed of pentyl valerianate, C^HoCOOC.^Hji. 

Experiment No. 12 — Esters 

Reading— P. & K. pp. 174, 188-193. 

N. pp. 278-280. 



ESTERS 35 

Apparatus. 2 test-tubes, Bunsen burner. 

Material. Alcohol, acetic acid, cone, sulphuric acid, 

butyric acid. 

Ethyl Acetate. In a test-tube mix 5cc. of alcohol 
with an equal amount of acetic acid; add a few drops of 
cone, sulphuric acid and warm gently. Notice the odor. 

CHsCOOH+C^HgOH-^CHgCOOC^Hs+H^O. 

Ethyl Butyrate. Place one drop of butyric acid in 
5cc. of water, add a few drops of cone, .sulphuric acid and 
then Ice. of alcohol. Mix and warm gently. Ethyl butyrate 
has the odor of pineapple. Do you distinguish this odor 
in the test-tube ? 

C3H,C00H+C2H50H^C3H,C00C2H5+H20. 



CHAPTER VIII. 
Fats 

Fats. The fats are glyceryl esters of the fatty acids. 
They may be represented by the general formula 
(RC00)3C3H,. 

When saponified the fats yield the free fatty acid, or 
its salt, and glyceMne. Glycerine it will be remembered 
is a trih3^dric alcohol. 

Fat Fatty acid Glycerine 

(RrOO)3L;H3+3H,0-^3RCOOH + CsH^COH)^ 

The most important fats are stearin, 
(C,,H35COO)3C3H„ palmitin, (C,5H3iCOO)3C3H5, and 
olein, (Ci7H33COO)3C3H5. These occur in the animal fats 
such as suet, tallow, lard, and butter, and in many of the 
vegetable fats such as sesmane oil, cottonseed oil, peanut 
oil, etc. Stearin does not occur in olive oil but the other 
fats do. 

Experiment No. 13. — Fats 

Reading— P. & K. pp. 169-174. 

Leach, pp. 471-480. 

Sherman, pp. 16-17, pp. 20-23. 
Apparatus. Basin, capillary tubes, thermometer, beak- 
ers, test-tubes, Bunsen burner. 

Material. Tallow, lard, suet, butter, olive oil, muslin bag, 
soap solution, alcohol, chloroform, ether, benzene, 
litmus paper, potassium bisulphate. 

Tests. 

1. — Melting Point. Place a muslin bag containing 
about 2g. of tallow in a pan of hot water and squeeze out 
the melted fat : allow the water to cool, then skim off the 



FATS 37 

solid fat from the surface. Dry the fat between filter 
paper. Refine a small amount of suet in the same way. 
Determine the melting point of the suet and tallow and, 
also, of some butter and lard as follows: 

Place a beaker partly filled with water in a second 
beaker of water, the two vessels being separated by 
pieces of cork. Fill a capillary tube with the fat which 
is to be tested ; attach the capillary tube to a thermometer 
inserted in a cork; suspend thermometer in the inner 
beaker of water. Now gently heat the beakers of water 
over a wire gauze and note the temperature at which the 
fat melts. 

Fill out the following record: 

Fat Melting Point 



Lard 




Tallow 




Butter 




Suet 





2. — Solubility. Test the solubility of olive oil in hot 
and cold water, in soap solution, and in alcohol, chloro- 
form, ether and benzene. (Avoid flame when using 
alcohol, ether and benzene.) 

3. — Rancidity. Test the reaction of some old olive 
oil and old butter to litmus paper. 

4. — Acrolein Test. Grind up a small piece of tallow 
in a mortar with an equal bulk of dry potassium bisul- 
phate ; transfer to a test-tube and heat until dense white 
fumes are evolved. Observe the odor of the fumes taking 
care however not to get them in the eyes. The irritating 
odor of the fumes is due to acrolein, a product resulting 
from the decomposition of glycerine. Do you get this 
<5ame odor when fats are heated too strongly? 

Questions. 

1. What causes fats to become rancid? 
2. — What is "process" butter? 



38 FATS 

3. — What is oleomargine ? Is it a good substitute for 
Dutter ? 

4. — Of what are the "compound" lards composed? 

5. — What chemical compound is formed when fats 
are too highly heated as sometimes happens in deep fat 
cookery ? 

6. — How would you remove a grease stain from non- 
washable fabrics? 



CHAPTER IX. 
Soap and Glycerine 

Soaps. When fat is boiled with a solution of sodium 
or potassium hydroxide the fat is hydrolized with the for- 
mation of soap and glycerine. If the alkali used is po- 
tassium hydroxide, soft soap is formed. If sodium hy- 
droxide is used a hard soap will result. Both the animal 
fats and vegetable oils are used in soap making. The 
vegetable oils produce a less caustic soap. 

Glycerine. Glycerine is formed when fats are 
saponified. After the soap is removed the watery solu- 
tion is evaporated and the glycerine is purified by distilla- 
cion under diminished pressure. Glycerine is a sweet 
colorless syrup which mixes with water and alcohol in 
every proportion. When glycerine is heated with a de- 
hydrating substance, such as potassium bisulphate, it un- 
dergoes decomposition into water and acrolein. Acrolein 
IS an aldehyde. 

Acrolein reaction 
Glycerine Acrolein 

C3H, ( OH) 3-^CH2.CH.CHO+2H,0 

Experiment No. 14. — Soap and Glycerine 

Reading— P. & K. pp. 171-172. 

Apparatus. 500cc. flask, evaporating dish, stirring rod, 
burner, ring-stand, beaker, 4 test-tubes. 

Material. Lard, alcohol, potassium hydroxide, 90 per 
cent alcohol, absolute alcohol, dilute sulphuric acid, 
sodium carbonate, potassium bi-sulphate, calcium 
sulphate solution, magnesium sulphate solution, 
dilute hvdrocliloric acid. 



40 SOAP AND GLYCBHINE 

Saponification of Lard. Dissolve 25g. of lard in an 
equal volume of alcohol by warming in a flask on a water 
bath, add 75ec. of alcoholic potassium hydroxide, (lOg. 
of potassium hydroxide dissolved in lOcc. of water and 
diluted to 75cc. with 90 per cent alcohol), and heat on 
the water-bath until all the fat is saponified. This can be 
ascertained by pouring a drop or two of the mixture into 
a test-tube of water. When saponification is complete the 
mixture will dissolve with no separation of free fat. 
Now transfer the solution from the flask to an evapora- 
ting dish containing lOOcc. of water and heat on the 
w^ater-bath until all the alcohol is driven off. Acidify 
the solution with dilute hydrochloric acid, and cool. The 
fatty acids separate out and rise to the surface. Skim 
off the precipitated fatty acids and save for the prepara- 
tion of soap. Save the solution in the evaporating dish 
for the extraction of glycerine. 

(C,,H3,COO)3C3H,+3H,0^3C,,H3,COOH+C3H,(OH)3 

Preparation of Soap. Melt the precipitated fatty 
acids in a beaker on the water-bath; add, gradually with 
constant stirring, a half saturated solution of sodium car- 
bonate until the fatty acids have dissolved. This will 
take some time. Avoid an excess of sodium carbonate. 
As soon as solution has taken place, allow to stand until 
cold. The solid residue is soap." Press into a cake and save 
for tests. 

2Ci,H,.,COOH+NaX03-^2Ci5H3iCOONa+H20+C02 

Tests for Soap. Dissolve a portion of the soap in 
water and use this solution for the tests. 

1. — Place 5cc. of the soap solution in a test-tube and 
add a few drops of dilute sulphuric acid. The curdy pre- 
cipitate is free fatty acid. 

2. — To 5cc. of the soap solution in a test-tube, add a 
few drops of calcium sulphate solution. The precipitate 
is a calcium soap. 

3. — Eepeat test 2, using magnesium suphate solution 



SOAP AND GLYCERINE 41 

instead of calcmm sulphate. What is the effect of hard 
water on soap solutions? 

Extraction of Glycerine. Use the solution saved 
from the saponification test. Neutralize the solution \Vith 
sodium carbonate and evaporate to dryness on the water- 
bath. Extract the residue with absolute alcohol, remove 
the alcohol by evaporation on the water-bath, and, with 
the residue of glj^cerine thus obtained, make the tests giv- 
en below. 

Tests for Glycerine. 

1. — Describe the taste of the glycerine. 

2.— Place some of the glycerine in a dry test-tube 
and add a pinch of dry potassium bisulphate. Heat cau- 
tiously and notice the fumes of acrolein which are 
evolved. Avoid getting the fumes into the eyes. 

Questions. 

1. — How is soap made in the home? 

2. — How are toilet soaps made? 

3. — To what is the cleansing action of soap due? 

4. — Why should hard water be softened before being 
used for laundry purposes? How may water be softened? 



CHAPTER X. 

Simple Sugars 
Carbohydrates. The sugars are the simplest of the 
carbohydrates. All the carbohydrates are called sacchar- 
ides. The simple sugars are called monosaccharides. 
The more complex sugars are grouped as di- and 
tri-.saccharides according as they yield two or three 
molecules of monosaccharides on decomposition. Car- 
bohydrates which decompose into several molecules of 
monosaccharide compounds are named polysaccharides. 

Classification of Carbohydrates. 

Sugars. 

I. Monosaccharides: pentoses, hexoses (glucose, 
fructose, etc.) 

II. Disaccharides : cane sugar, malt sugar, milk 
sugar, etc. 

III. Trisaccharides : raffinose. 

IV. Polysaccharides. 

1. Starches. 

2. Gums. 

3. Celluloses. 

Monosaccharides. The monosaccharides or simple 
sugars, are aldehyde or ketone derivatives of polyhydric 
alcohols. They are named from the number of carbon 
atoms which they contain and are given the terminal end- 
ing ose. Thus, sugars whose molecules are built up of six 
carbon atoms are called hexoses, those containing five are 
pentoses, etc. The most important group of the mono- 
saccharides is the hexose, CeHigOs, group to which glucose 
and fructose belong. 

Glucose. Glucose, or grape sugar, formerly called 
dextrose, occurs in many sweet fruits and in honey. It is 
found in the urine in cases of Diabetes mellitus. It is 
formed when the polysaccharides, (cane sugar, starch, 



SIMPLE SUGARS 43 

cellulose), are hydrolized. It is also formed by the decom- 
position of the glucosides. Glucose is prepared commer- 
cially by boiling starch with dilute sulphuric acid. 

Glucose crystallizes from water in nodular masses, 
melting at 86°. It is soluble in its own weight of water. 
Glucose is not as sweet as cane sugar. 

Glucose is an aldehyde sugar. 

Glucose resembles both aldehydes and polyhydric 
alcohols in its chemical behavior. It shows the following 
characteristic aldehyde reactions: 

1. — On reduction glucose is converted into a hexa- 
hydric alcohol. 

2. — On oxidation glucose is converted into an acid 
containing six carbon atoms, gluconic acid. 

3. — Glucose precipitates cuprous oxide from alkaline 
cupric solutions. 0.05 grams of glucose exactly reduce 
lOcc. of Fehling's solution. 

4. — Glucose reduces an ammoniacal solution of silver 
nitrate. 

5. — With excess of phenylhydrazine glucose forms 
glucosazone. 

Glucose resembles the alcohols in that it reacts with 
organic acids to form esters, the most important of which 
are the glucosides obtained from plants. Salicin, 
amygdalin, coniferin, and tannins are examples of 
glucosides. The tannins are grape-sugar esters of the 
tannic acids. 

Glucose ferments readily with yeast yielding alcohol 
and carbon dioxide as the main products. Under the in- 
fluence of certain bacteria glucose undergoes a lactic 
acid fermentation. This is the fermentation which occurs 
in the souring of bread, the souring of milk and in the 
manufacture of dill pickles and sauerkraut. 

Alcoholic fermentation 
glucose zvmase alcohol car])on dioxide 
OeH,,0, ' > 2 C^H.OH + 2CO2 



44 SIMPLE SUGAlg-S ' 

Lactic acid fermentation 

lactic acid 
glucose ferment lactic acid 

Glucose is most frequently placed on the market in 
the form of a syrup. It is used extensively in the manu- 
facture of jellies, jams, confectionery and canned pro- 
ducts. 

Fructose. Fructose, fruit sugar, levulose, C6Hi20e, 
occurs together with glucose in almost all sweet fruits. 
It may be obtained by the hydrolytic decomposition of 
inulin, a starch found in the roots of the dahlia and some 
other plants. It is formed in equal amounts with glucose 
when cane sugar is hydrolized. Fructose is a ketone 
sugar. 

Fructose is more soluble in water than glucose and 
crystallizes less readily. It separates out from alcohol in 
small hard crystals which melt at 95°. 

Fructose resembles glucose in chemical behavior. It 
reduces Fehling's solution to the same extent as glucose. 
With excess of phenylhydrazine it forms glucosazone. It 
differs from glucose in the solubility of its lime com- 
pound. On oxidation fructose gives the characteristic 
ketone reaction, i. e. forms acids of less carbon content. 
Fructose when oxidized with nitric acid gives glycoUio. 
acid, CH.OH, and tartaric acid, CHOHCOOH. 

I " -I 

COOH CHOHCOOH 

Experiment No. 15— Glucose and Fructose 

Reading— P. & K. pp. 266-274. 

N. pp. 357-366. 

Sherman pp. 4-9. 
Apparatus. 4 beakers, water-bath, carbon di-oxide gen- 
erator, 6 test-tubes, 2 evaporating dishes, burner. 



SIMPLE SUGARS 45 

Material. Sugar, dilute sulphuric acid, chalk, slaked 
lime, ice, filter paper, cone, hydrochloric acid, mar- 
ble, Fehling's solution, potassium hydroxide, lime 
water, glucose, phenylhydrazine hydrochloride, sod- 
ium acetate, cone, sulphuric acid, honey, raisins, ap- 
ples. 

Preparation of Glucose and Fructose. Dissolve lOg. 
of sugar in 50cc. of water in a beaker and add 15cc. of 
dilute sulphuric acid; heat on a water-bath at 70° for 20 
minutes ; cool, exactly neutralize with chalk ; filter off 
the precipitated calcium sulphate. Place filtrate in a 
beaker, cool with ice, and add 6g. of slaked lime, in small 
quantities at a time, stirring constantly. Keep the beak- 
er cold and allow to stand for a few minutes. The lime 
compound of fructose is insoluble and will separate out 
as a pasty precipitate. Filter and use precipitate for 
fructose extraction and filtrate for the extraction of 
glucose. Label the filtrate A, and save until you are ready 
to extract glucose. 

Suspend the lime-fructose precipitate in 50cc. of 
water in a beaker and run in carbon di-oxide gas until 
the mixture is no longer alkaline. Filter off the precipi- 
tated calcium carbonate, and evaporate the filtrate to a 
thick S3^rup on a water-bath. The syrup consists of nearly 
pure fructose. Use this syrup for the fructose tests. 

Extract the glucose from filtrate A by passing in 
carbon di-oxide gas until the solution no longer reacts 
alkaline ; then filter and evaporate to a thick syrup on 
the water-bath. Use syrup for glucose tests. 

cane sugar water glucose fructose 

CisHogOii + H2O -^ CgHioO,; + CgHjoOe 

Tests for Glucose. 

1. — Taste the glucose syrup and compare sweetness 
with that of cane sugar. Dissolve the syrup in about 
lOcc. of water and use the solution for tests 2, 3 and 4. 



40 SIMPLE SUGAJIS 

2. — To about 2c c. of the glucose solution add a few 
drops of cone, sulphuric acid. Does any change occur? 
Warm and notice that the solution becomes yellow at 
first and finally darkens. 

3. — Add a few drops of the glucose solution to 5cc. of 
Fehling's solution in a test-tube. Boil and describe the 
changes which take place. Is the color due to the pre- 
cipitate, or to the solution? 

4. — Add a few drops of clear lime water to about 5cc. 
of the glucose solution. Mix well. Is there a precipitate 
formed ? 

5. — Dissolve Ig. of solid glucose, (grape-sugar), and 
3g. of sodium acetate in 20cc. of water in a beaker; add 
2g. of phenylhydrazine hydrochloride and mix well. 
Heat the mixture on the water-bath at boiling tempera- 
ture for 20 minutes. On cooling a yellow crystalline 
precipitate, glueosazone. is obtained. 

Tests for Fructose. 

Repeat tests 1, 2, 3 and 4, given under glucose, using 
the fructose syrup and solution instead of glucose. In 
what way does fructose differ from glucose? 

Tests for Glucose and Fructose in Foods. 

Make a water extract of raisins, of honey, and of ap- 
ples. In each case test the solution with Fehling's solu- 
tion. Do these substances contain reducing sugars? 

Questions. 

1. — Of what importance is glucose commercially? 
How is commercial glucose prepared? 

2. — What is corn syrup? 

3. — Are candies and preserves made of glucose 
wholesome ? 

4. — Would glucose or fructose be a good substitute 
for cane sugar? 



SLMPI.K SUGARS 47 

Experiment No. 16. — Determination of the Amount of 
Reducing Sugar in a Sample of Syrup or Molasses 

Eeading. — Leach, pp. 590-593. 

Apparatus. 2 100 cc. graduated flasks, 2 burettes, 
Erleiiiiieyer flask (250 cc), ring-stand, wire gauze, 
burner. 

Material. — Syrup or molasses, lead subacetate solution, 
sodium sulphate solution, standard Fehling's solu- 
tion, anhj^drous dextrose. 

Standardization of Fehling's Solution. 

Make up Fehling's solution in tAvo parts as follows: 

A. Fehlmg s C opper Solution. — 34.639 g. of crystals 
of pure copper sulphate, powdered, dissolved in water 
and diluted to exactly 500 cc. . 

B. Fehling's Alkaline Tartrate Solution— 173 g. of 
Eochelle salts and 50 g. of sodium hydroxide dissolved in 
water and diluted to exactly 500 cc. . 

Dissolve 0.5 g. of pure anhydrous dextrose in a 
little water in a 100 cc. graduated flask and dilute to 
exactly 100 cc. Mix thoroughly and fill a clean, dry 
burette with this solution. With pipettes add 5 cc. of 
Fehling's solution A, and 5 cc. of solution B to a 250 cc. 
Erlenmej^er flask ; add 40 cc. of water and boil over 
a wire gauze. While still boiling, add from burette a 
measured quantity of the dextrose solution. Boil three 
minutes after each addition of dextrose. Run in the 
dextrose solution until the copper is all reduced to 
cuprous oxide. The end-point must be very carefully de- 
termined. As the sugar is added and the solution boiled, 
several changes of color occur; the solution is first deep 
blue, then appears to be green, dull red and finally brick 
red. The green and red color is produced by the pre- 
cipitate. The solution is blue as long as there is any 
unreduced copper; when all the copper has been reduced 
to cuprous oxide, the solution becomes colorless or yel- 
low. The difficulty in determining the end point exactly 
is due to the fact that the red precipitate obscures the 



48 SIMPLE SUGARS 

real color of the solution. Leach, (Food Analysis, pp. 
591, 592,), recommends that, as soon as the dull red tint 
is obtained, the sugar be added a little at a time ; after 
each addition has been added and boiled he recommends 
that the flask be removed from the flame and the bright 
diffused light from a window be viewed through the 
solution with the eye on a level with the surface. If 
this is done a thin line will be observed just below the 
surface of the solution. This line will be blue as long as 
there is unreduced copper in the solution. When, however, 
all the copper ha^been reduced, this line ceases to be blue 
and becomes yellow or colorless. 

When the end point has been reached, calculate the 
strength of your Pehling's solution in grams, of glucose. 
If 0.5g. of dextrose are diluted to 100c c. Ice. of the solu- 
tion will contain how many grams of dextrose ? 

lOcc. of your Fehling's solution are equivalent to 
how many grams of dextrose ? 

lOcc. Fehling's solution = ? g. dextrose 



Determination of the amount of reducing sugar (calcu- 
lated as dextrose), in a sample of syrup or molasses. 

Weigh 5g. of molasses or syrup into a lOOcc. grad- 
uated flask. Dissolve in a little water. In the case of 
molasses or "golden". syrup it is necessary to decolorize 
by the addition of lead subacetate solution. Add from 
2 to 5cc. of the subacetate solution to precipitate the 
coloring matter. Make up to the lOOcc. mark with water, 
filter; take 25cc. of the filtrate and, if lead subacetate 
has been added, precipitate the excess of lead with so- 
dium sulphate solution; filter; then dilute to lOOcc. with 
water. This diluted solution should not contain more 
than 1/2 pel* cent of dextrose. Fill a clean, dry burette 
with this solution and determine how much it 
takes to reduce exactly lOcc. of Fehling's so- 
lution. Make the, determination in the same way as in the 
standardization of the Fehling's solution. Determine the 



SIMPLE SUGARS 49 

end-point carefnlly. Prom the data at hand calculate the 
amount of reducing sugar, (dextrose), in the syrup. 

Substitute your own figures and tabulate the result 
as follows: 

10 cc. of Fehling's solution = ... .no. cc. of syrup 

solution 
10 cc. of Fehling's solution = 0.05 grams of dextrose 
. . . .no. cc. of syrup solution=0.05 grams of dextrose 

1 cc. of syrup solution^ grams of dextrose 

Syrup solution^? per cent dextrose 



CHAPTER XI 

Disaccharides 

Cane Sugar. Cane sugar, sucrose, C12H22O11, is by 
far the most important of all the sugars. The annual con- 
sumption amounts to about 80 pounds per capita. It is ob- 
tained from the sugar cane, sugar beet, sorghum cane, 
and from maple sap. It occurs in the juice of sweet 
fruits, such as the pine-apple, in vegetables, such as the 
carrot, and in all cereals. 

Cane sugar is very soluble in water and crystallizes 
out in well defined prisms. When melted and allowed to 
cool it forms a clear yellow mass called barley sugar. 
Barley sugar slowly changes back to the crystalline form. 

At high temperatures cane sugaT is decomposed 
yielding water and carbon. The first stage in its de- 
composition results in the formation of caramel. 

Disaccharide sugars are so named because, when 
boiled with acids, or acted upon by ferments, they yield 
two parts of a monosaccharide sugar. Cane sugar forms 
glucose and fructose. 

cane sugar glucose fructose 

C12H22O114-H2O -^ CeHi206 -|- CeHjgOe 

This reaction is spoken of as the inversion of cane 
sugar and the resulting mixture of glucose and fructose 
is called invert sugar. In cookery the inversion occurs 
whenever cane sugar is cooked with acid substances such 
as vinegar, fruit juices, or cream of tartar. Invert sugar 
does not crystallize as readily as cane sugar. 

Cane sugar does not ferment directly but must first 
be inverted. Ordinary yeast secretes a ferment, invertase, 
which causes the inversion. The invert sugar then under- 



DISACCHARIUES 51 

goes alcoholic fermentation through the influence of an- 
other ferment, zymase. 

zymase 
2C6H,20e > 4C2H5OH+4CO2 

Experiment No. 17. — Cane Sugar 

Keading-P. & K. pp. 274-276. 
N. pp. 367-370. 
Sherman, pp. 9-11. 
Apparatus. Porcelain or enamel casserole (% pint), 4 
test-tubes, beaker, burner, ring-stand, wire gauze, 
candy thermometer. 
Material. Sugar, Pehling's solution, dilute hydrochloric 
acid, sodium hydroxide, concentrated sulphuric acid, 
yeast. 

Tests : Prepare an aqueous solution of sugar and use for 

the first four tests. 

1. — To 5cc. of sugar solution add an equal volume 
of concentrated sulphuric acid. What is the result ? How 
does glucose differ from cane sugar in respect to this 
test? 

2. — Add a few drops of the sugar solution to lOec. of 
Fehling's solution and heat. Is cane sugar a reducing 
sugar? 

3. — To 5cc. of sugar solution add Ice. of dilute hy- 
drochloric acid and boil for a few minutes. Cool, neutra- 
lize with a few drops of dilute sodium hydroxide 
and test with Fehling's solution. What change has 
taken place in the sugar? 

4. — Add a little yeast to about 5cc. of the sugar solu- 
tion in a test-tube ; mix well and allow to stand for 15 
minutes; filter and test with Fehling's solution. In- 
vertase, an enzyme secreted by yeast, acts upon cane 
sugar converting it into glucose and fructose. 

5. — Carefully heat some sugar in a casserole until 



52 DISACCHARIDES 

the sugar just melts. Stir to prevent burning. With a 
candy thermometer, (or ordinary high temperature ther- 
mometer), ascertain the temperature of the melted sugar. 
Pour isome of the melted sugar on a glass plate ; when 
cool, examine and taste. 

6. — Heat the remainder of the sugar in the casserole 
to about 200°. As soon as the substance appears to boil, 
remove from flame, cool, examine and taste. What is 
formed ? 

Questions. 

1. — How is'caramel prepared? For what is it used? 

2. — -What is peanut "brittle"? 

3. — In making jelly is it better to add the sugar in 
the beginning, or after boiling the juice? 

■/ 4. — Why is cane sugar added to the dough in mak- 
ing-bread? Could glucose be added instead? 

5. — Why is cream of tartar added in making fon- 
dant? 

6. — Is cane sugar superior to the same grade of beet 
sugar? Describe the commercial preparation of each. 

7.— What is powdered sugar? Is it less sweet than 
granulated sugar? 



Malt Sugar. Malt sugar, maltose, C12H22O11, is 
formed by the action of malt diastase on starch. Malt 
diatase is a ferment which occurs in germinating grains, 
especially barley. . 

malt 
starch diastase maltose dextrin 
3(CeH,oO,)n+nH30 >r,C,Jl,,0,,+nC,,TL,,0,, 

The same reaction occurs during digestion under 
the influence of ptyalin and amylopsin. 

Maltose ferments readily with yeast yielding alcohol 
and carbon dioxide as the chief products. 

maltose water alcohol carbon dioxide 

C,2H220„+H20^4 C2H5O H + 4CO2 



DISACCHARIDES 53 

Experiment No. 18— Malt sugar 

Reading.— P. & K. pp. 276-277. 
N p. 370. 
Sherman, p. 11. 

Apparatus. Pan, water-bath, evaporating dish, test-tube. 

Material. Barley, filter paper, Fehling's solution. 

Preparation. Line a pan or pneumatic trough with moist 
filter paper; cover the bottom of the pan with bar- 
ley, moisten well, and keep in a warm place for two 
or three days. Do not allow the barley to become 
dry. When the barley is well sprouted, remove 
from pan, and dry in the oven or on a sand bath. Be 
mreful not to heat the sprouts over 100°. Cover the 
dry sprouts with water and macerate in a mortar; 
strain through muslin, then filter. Use filtrate for 
tests. 

Tests. 

1. — Place 5cc. of the filtrate in a test-tube and make 

Fehling's test. 

2. — Evaporate the remainder of the filtrate to a 

thick syrup over the water-bath. Study the properties 

of the syrup. 

Questions. 

1. — Of what commercial value is malt sugar? 
2. — How is malt sugar manufactured? 

Milk Sugar. Milk sugar, lactose, C^Ji^oOi^, is 

sometimes called animal sugar because, so far as is known, 
it occurs only in the animal kingdom. It is obtained from 
milk as a by-product in the manufacture of cheese. 

Milk sugar differs materially from cane sugar both 
in physical and chemical properties. When boiled Avith 
acids it yields glucose and galactose. 

lactose glucose galactose 

C,,H,,0,,+H,O^C,H,,Oe+CeH,,0, 

Milk sugar does not ferment with yeast. Under the 
influence of a ferment secreted by certain bacteria, which 



54 DISACCHARIDES 

are normally present in milk, it undergoes lactic acid 
fermentation. 

lactose lactic acid 

Ci2Ho20,i+H,0->4C3H603 

Experiment No. 19. — Milk sugar 

Reading.— P. & K. p. 277. 
N. p. 370. 
Sherman, p. 11. 

Apparatus. Beaker, water-bath, ring-stand, burner, test- 
tube, evaporating dish, glass rod. 

Material. Milk, rennet extract, Fehling's solution. 

Extraction From Milk. Place a beaker containing 500ec. 
of milk in a water-bath and warm to about 40° ; add 
10 drops of rennet extract to the milk and let stand 
in the warm water until a solid clot forms. Break 
the clot up with a glass rod and separate curd from 
whey by straining through a muslin cloth. Put whey 
in a beaker and boil over a wire gauze until the al- 
bumin is precipitated; filter, and evaporate the fil- 
trate to a thin syrup on the water-bath. Allow the 
syrup to stand until crystallization occurs. Use the 
crystallized product for the tests. 

Tests. 

1. — Taste some of the milk sugar and compare sweet- 
ness with cane sugar. 

2. — Dissolve some of the sugar in water and make 
Fehling's test. 

Questions. 

1. — How is the milk sugar of commerce obtained? 
2. — Can milk sugar be obtained from sour milk? 
3.— Why is milk sugar added in modifying cow's 
milk for infants? Could cane sugar be used instead? 



CHAPTER XII 

Starches 

Starch. Ordinary starch, amylum, (CsHjoOg) „' oc- 
curs in all green plants. It is stored in the seeds, roots 
and tubers of plants. We obtain it from cereals, from 
corn, and from potatoes and arrow root. It is in the 
form of minute granules consisting of starch cells in- 
closed in a cell wall. The physical structure of the 
granules is different in different plants. By means of 
the microscope we may determine the source of the 
starch, that is, whether it is from corn, potato, or some 
other plant. The microscope is of value in detecting the 
use of starch as an adulterant in foods. 

Starch is insoluble in cold water. "When boiling wa- 
ter is poured over starch the granules are broken and 
the contents dissolve. The cellulose walls of the granules 
remain in suspension in the solution and form a gelatinous 
mixture called starch paste. 

Dry heat converts starch into dextrin. The dex- 
trins are gums. They dissolve in water rorming a muci- 
laginous solution. Several dextrins are known, amylodex- 
trin which gives a purple color with iodine solution, 
erythrodextrin which reacts with iodine to form a ma- 
hogany-red coloration, and achroodextrin which is color- 
less with iodine. Dextrins are intermediate products 
formed in the conversion of starch into sugar. Some 
dextrinization always occurs when starch foods are 
baked. 

When starch solution is boiled with an acid the 
starch is converted into dextrin, maltose, and finally 
glucose. Commercial glucose which is prepared in this 
way is generally a mixture of these three compounds. 

Starch gives a characteristic reaction with a solu- 
tion of iodine in potassium iodide. This reaction is made 
use of in the identification of starch. 



56 STARCHES 

Experiment No. 20. — Starch 

Heading.— P. & K. pp. 278-280. 
N. p. 373. 
Sherman, pp. 12-14. 

Apparatus. Pan, beaker (8oz.), beaker (6oz.), evapora- 
ting dish, 4 test-tubes, glass slides, microscope, mor- 
tar. 

Material. Potatoes, iodine solution (2g. of iodine and 4g. 
of potassium iodide in lOOec. of water), Fehling's 
solution, dilute hydrochloric acid, cone, nitric acid, 
bread, corn, 'sago, rice, bean, arrow-root starch. 

Extraction. — Grate 4 medium sized potatoes and place 
the pulp in a muslin bag in a pan of water; squeeze 
out the milky juice. Allow to stand until the 
starch has settled to the bottom of the pan, then 
pour off the water, and wash the istarch by decanta- 
tion. Dry the starch between filter paper and use 
for tests. 

Tests. 

1. — Prepare a starch solution as follows: Make a 
paste of Ig. of .starch and 2cc. of water in a mortar; 
pour the paste into lOOcc. of boiling water in a beak- 
er. The starch granules are insoluble but heat ruptures 
the walls of the granules freeing the contents which dis- 
solve. The cell walls remain in suspension in the liquid 
and thus give an opalescent solution. Save this starch 
solution for the tests. 

2. — To 5cc. of cold starch solution in a test-tube add 
a drop of iodine solution and mix well. What is the re- 
sulting color? This color is characteristic of starch 
and iodine solution. It is due to the formation of an io- 
dide of starch, an unstable compound easily decomposed 
by heat. Heat and observe the effect. 

3. — Test 5cc. of the starch solution with Fehling's 
solution. 

4. — Mix 20cc. of the starch solution and 5cc. of di- 
lute hydrochloric acid in a beaker and boil gently, over 



STARCHES 57 

a low flame, for half an hour; cool and neutralize with 
sodium hydroxide. Make Fehling's test with a portion 
of the solution. 

5. — To 2g'. of starch in an evaporating dish add 1 
drop of concentrated nitric acid; heat on a sand bath, 
stirring constantly, until the mixture becomes light 
brown in color. When this occurs, remove from flame 
and dissolve a portion of the mixture in a small amount 
of water ; filter into a test-tube and add a drop of iodine 
solution. The color is due to dextrin. It varies from 
purplish to mahogany red depending upon how far the 
dextrinization has proceeded. 

6. — Toast a small piece of bread on wire gauze over 
a low flame. When well browned, grind up with water 
in a mortar, filter and test the filtrate with a drop of io- 
dine solution. Does the toast solution give the dextrin 
reaction ? 

7. — Study the starch granules of potato, corn, rice, 
sago, bean, and arrow-root under the low and high pow- 
er of the microscope. Prepare the slides as follows ; 
Grind a little of the substance with a little water in a 
mortar; with a glass rod take up one drop of the watery 
mixture and spread evenly on a glass slide ; cover with 
cover glass and examine. Make drawings of the different 
granules as they appear under the microscope. 

Questions. 

l.^What is the difference between the starch used 
for food and that which is used for laundry purposes? 

2.— How could you prepare a soluble starch for 
laundry use, i. e., a starch which will dissolve in cold 
water ? 

^ 3. — Which would be most easily digested, potato or 
rice starch ? 

4. — Why is arrow-root starch recommended for in- 
valids' dietaries? 

5. — Why is the part of the baked potato next the 
skin sweeter than the rest? 

6. — What digestive value has ''zwieback? 



58 STARCHES 

Glycogen. Glycogen, animal starch, is the form in 
which carbohydrates are stored in the body. It is found 
principally in the liver and muscle cells. It constitutes 
a reserve food supply which may be used for the libera- 
tion of heat and energy. Before glycogen can be used 
by the body it must be converted into a soluble form, 
glucose. This is accomplished by means of a diastase 
found in the cells of the liver and muscles. Glycogen al- 
so occurs in some of the fungi, i. e., plants without chlor- 
ophyll, such as yeast. 

Glycogen, lil^e ordinary starch, yields glucose when 
boiled with acids. With iodine solution glycogen gives a 
port wine coloration. The constitution of glycogen is 
probably much less complex than that of ordinary starch. 

Experiment No. 21. — Glycogen 

Reading.— P. & K. p. 564. 
N. p. 374. 
Sherman, pp. 14-16. 

Apparatus. Casserole (500cc.), ring-stand, burner, wat- 
er-bath, 2 beakers, 3 test-tubes. 

Material. Fresh liver, alcohol, iodine solution, Fehling's 
solution, dilute hydrochloric acid, muslin cloth. 

Extraction. Add 50 g. of minced liver to a casserole, or 
large beaker, and cover with 200cc. of water; boil 
for 20 minutes, then strain through muslin and filter. 
Concentrate the filtrate on the water bath to about 
50cc., cool, and precipitate the glycogen by the addi- 
tion of lOOcc. of alcohol. When the glycogen has 
settled out, filter and wash the precipitate with a 
little alcohol. Dissolve the precipitate in water and 
use this solution for the tests. 

Tests. 

1. — Make Fehling's test with 5cc. of the solution. Is 
there any reduction? 

2. — Boil about 5cc. of the solution with a few drops 
of dilute hydrochloric acid for a few minutes; cool, neu- 
tralize with sodium hydroxide, and make Fehling's test. 



STARCHES 59 

3. — Add a drop of iodine solution to some of the gly- 
cogen solution. The color is due to the compound formed 
by the iodine and glycogen. 

Questions. 

1. — Why is glycogen called animal istarch? Do veg- 
etable cells ever contain glycogen? 

2. — What is the function of glycogen in the body? 

3.— Which foods yield glycogen in the body? 

4. — In the laboratory experiment why must fresh 
liver be used? 



CHAPTER XIII 

Pectin 

Pectin. Pectin is the substance in fruits and vege- 
tables which gives them their jelly forming properties. 
It exists in considerable quantity in most ripe fruits and 
in many vegetables. Apples, plums, currants, grapes and 
other fruits, as well as carrots and potatoes 
contain a large ' amount of pectin. The pectin is 
generally in the juice and pulp of the food 
but in some instances it is found in the skin. Miss 
Goldthwaite^ claims that in oranges and lemons the pectin 
is in the white inner skin lining the peel. 

Pectin swells up and dissolves in water forming a 
viscid liquid which tends to gelatinize when its solutions 
become at all concentrated. The object in jelly making 
is to prepare a liquid of such concentration that this gel- 
atinization will occur. The factors influencing the gela- 
tinization are the amount of water, the amount of sugar, 
and the amount of acid in the fruit juice. When the 
fruit juices are boiled a considerable aiiiount of water is 
evaporated off. Tn making jelly then the solution must 
be boiled until the right concentration is obtained. This 
is determined by the "jell" test, i. e. allowing the solu- 
tion to boil until it jells when dropped from a spoon. 
The amount of sugar added to the fruit juice in making 
jelly must be proportional to the amount of pectin in the 
juice. Miss Goldthwaite* gives a method for determin- 
ing this proportion. The fruit juice must have a certain 
amount of acid in order to make a good jelly. Frequent- 
ly jelly is made from non acid fruits by mixing these 
with acid fruits. 

*See Bulletin, Principles of Jelly Making by N. E. 
Goldthwaite, published by the Dept. of Household 
Science, The University of Illinois. 



PECTIN 61 

Experiment No. 22. — Pectin 

Reading. — Bui. Dept. of Household Science, University 

of Illinois — Principles of Jelly-making. — Goldth- 

waite. 
Apparatus. Mortar, 4 beakers, 4 test-tubes, 2 watch 

glasses. 
Material. Apple, carrot, alcohol, sugar, cheese cloth. 
Extraction. Cut an apple into small pieces and grind up 

in a mortar; place pulp in a beaker and add just 

enough water to cover; boil gently for 10 minutes; 

strain through 4 thicknesses of cheese cloth. Save 

juice for tests. 

Prepare some carrot juice by treating a carrot in the 
same way. Make the tests given below, first with the ap- 
ple juice and then with the carrot juice. 

Tests. 

1. — Allow 3cc. of the juice to stand in a test-tube for 
an hour. Does the juice gelatinize on standing? 

2. — Add a few drops of alcohol to a little of the 
juice in a test-tube. The precipitate contains the pectin 
which is insoluble in alcohol. 

3. — Weigh the remainder of the juice, add three- 
fourths the weight of sugar and boil gently from three to 
five minutes. Gauge the time by the concentration of 
the solution. After boiling pour the liquid on a watch 
glass and allow to cool. Do you get the formation of 
jelly in each case? 

Questions. 

1. — Why is fruit juice boiled in making jelly? 

2, — Can jelly be made from un-cooked fruits? 

3. — In making jelly is there any danger of boiling 
the fruit juice too long? 

4.— Why is sugar used in making jelly? 

5. — How could you make orange or lemon jelly? 

6. — If a fruit contains too little pectin for jelly for- 
mation, how may this be corrected? 



CHAPTER XIV 

Cellulose 

Cellulose. Cellulose, (CeH^oOs)!!, is the principal 
ingredient of the cell membranes of all plants. It is the 
most complex carbohydrate. It is obtained from plant 
fiber by treating successively with dilute potassium hy- 
droxide, dilute Ijydrochloric acid, water, alcohol, and 
ether, to remove all incrusting substances. 

Cellulose is insoluble in all the usual solvents. It 
dissolves in ammoniac al copper solution, (Schweitzer's 
reagent), from which solution it may be precipitated 
with acids. 

Cellulose swells up in concentrated sulphuric acid 
and dissolves forming dextrin. When this solution is 
diluted and boiled, glucose is formed. Cold concentra- 
trated nitric acid, or a mixture of nitric and sulphuric 
acids, converts cellulose into nitro-celluloses, which are 
used in the preparation of artifical silk, celluloid, collo- 
dion, and gun cotton. 

Vegetable parchment is formed when unsized filter 
paper is treated with dilute sulphuric acid. This is 
largely used as a substitute for ordinary parchment. 

Experiment No. 23. — Cellulose 

Reading.— P. & K. pp. 281-283. 
N. pp. 371-372. 

Apparatus. Beaker, glass rod, wire gauze, ring-stand, 
burner, glass slide, microscope, 3 evaporating dishes. 

Material. Cotton wool, concentrated sulphuric acid, con- 
centrated sodium hydroxide, Fehling's solution, 
good grade filter paper, linen. 

Tests. 

1. — Dissolve Ig. of cotton wool in 5cc. of concentra- 
ted sulphuric acid in a beaker, stirring well during the 



CELLULOSE 63 

operation. Wlieu the mass becomes semi-liquid, careful- 
ly add 15cc. of water and boil on a wire gauze over a low 
flame for 20 minutes. Replace the water lost by evapor- 
ation. After boiling, cool the solution, neutralize with 
concentrated sodium hydroxide solution, and make Feh- 
ling's test. By this treatment cellulose is partly conver- 
ted into dextrin and glucose. 

2. — The best grades of washed filter paper consist of 
cellulose which is practically pure. Separate a few fi- 
bers from some good grade filter paper and examine on 
a slide under the microscope. Make a drawing of the 
fibers as they appear under the microscope. 

3. — Examine some linen fibers under the microscope 
and compare with the fibers seen in test 2. 

4. — Prepare 3 evaporating dishes containing respect- 
ively concentrated sulphuric acid, water, and ammonium 
hydroxide solution. Dip a piece of unsized paper in the 
acid bath for an instant and then pass the strip rapidily 
through the water and the ammonia baths. Allow the 
strip to dry ; compare its strength with that of some pa- 
per which has not been so treated. 



CHAPTER XV.— Proteins 
Classification 

The classification of proteins which the committee 
on protein nomenclature recommend may be found in 
many text books.* , A tabulated list of the proteins which 
occur most commonly in our chief protein foods, i. e., 
milk, eggs, meat, and vegetables, is given below. 



Protein 



Solubility 



Occurrence 



Albumins 



05 

o 
Ph- 

a; 



C/} 



Globulins 



sol. in water 

sol. in dilute isalt 
solution and in 
dilute alkalies 



albumins of egg^ 
milk, meat 

globulins of egg, 
blood, meat^ 
edestin of wheat 



Glutelins 



sol. in dilute acid glutelin of flour 
and alkalies 



Ajlcohol, sol. 

proteins 
Albuminoids 



insol. in all neut- 
ral solvents 



gliadin of flour^ 
zein of corn 

collagen of bone^ 
keratin of skin, 
elastin of tis- 
sues, gelatin, 
fibroin of silk 



•l-H 

o 

(V 

4-3 

fs 

•r-s 

o 



Phosphoproteins sol. in dilute alka- casein of milk, 



lies 



vitellin of egg 
yolk, legumins 
ofpeasandbeans 



Nucleoproteins sol. in alkalies 



cell nucleus 
plant and 
mal cells 



of 
ani- 



Hemoglobin 



insol. in water 



hemoglobins of 
blood 



'Sherman, Chemistry of Food and Nutrition, pp. 26-29 



PROTEINS 65 

Protein Solubility Occurrence 



xn 


^Coagulated pro- 
teins 


insol. products resulting from the 
action of heat or alcohol on pro- 
teins 




Proteoses 
Peptones 


sol. in water but ppt'd by saturation 
with ammonium .sulphate, derived 
from proteins by hydrolysis 


> 


sol. in water, not ppt'd by satura- 
tion with ammonium sulphate — 
formed by digestion or hydroly- 
sis of proteins 



Proteins are the chief constitutents of living proto- 
plasm. They are formed exclusively in plant cells. They 
consist of carbon, hydrogen, oxygen, nitrogen and sul- 
phur, and some contain phosphorus also. The proteins 
are very complex compounds and have a high molecular 
weight. They are built up of anhydrides of the amido 
acids. 

The proteins differ greatly in solubility. With the 
exception of albumins they are generally insoluble in 
water. They are also insoluble in alcohol and ether. 
Most of them are precipitated by mineral acids, by al- 
kalies, by salts of the heavy metals, and by alkaloids. 
Many proteins are coagulated by heat. 

When proteins are hydrolized they yield a large 
number of products, chief of which are the amido acids. 
Some of the prominent amido acids formed by protein 
decomposition are glycin, CH2NH2COOH, alanin, 
CH3CHNH2COOH, leucin, (CH3)2CH.CH2CHNH2COOH 
and tyrosin, C6H4(0H)CH2CHNH2C00H. The amido 
acids all contain one or more amido, NHg, group. 

The proteins give certain characteristic color reac- 
tions with particular reagents. These color reactions are 
used in their identification. 



66 PROTEINS • 

Experiment No. 24. — Proteins 

Reading— P. & K. pp. 610-614. 
N. pp. 509-516. 
Sherman, pp. 23-40. 

Apparatus. 4 beakers, 2 flasks, 10 test-tubes, 2 evaporat- 
ing dishes, thermometer, ring-stand, burner. 

Material. Egg white, ammonium sulphate, sodium 
chloiide, alcohol, concentrated acids, concentrated 
alkalies, soluifcions of mercuric chloride, silver nitrate, 
lead acetate, copper sulphate, tannic acid, picric 
acid, ammonium hydroxide, Millon's reagent, milk, 
gelatine, peptone, litmus solution. 

I. Tests With Egg Albumin. 

Place the white of an egg in an evaporating dish and 
cut fine with a pair of scissors ; reserve a portion of the 
white for the tests which call for undiluted egg white; 
divide the rest of the egg white into two parts and dilute 
one part Avith water so as to form a 2 per cent solution ; 
dilute the other portion so as to form a 5 per cent solu- 
tion. Use the more dilute solution for all tests except 
these which call for the 5 per cent solution. 

1. — Coagulation, (a). Place 5cc. of the albumin 
solution in a test-tube and heat. Notice the coagulation. 
Repeat this test, first acidifing w4th a few drops of 
acetic acid. 

(b). Fit a test-tube with a perforated 
cork into which a thermometer has been inserted 
and fill the test-tube one third full ofundiluted egg white. 
Suspend the tube in a beaker of water and heat gradual- 
ly, stirring the water during the process. Note the tem- 
perature at which cloudiness occurs. Note the tempera- 
ture at which a solid clot forms. 

2. — Precipitation, (a). To 5cc. of the albumin 
solution add a few drops of concentrated hydrochloric 
acid. What occurs? Try the effect of strong nitric, sul- 
phuric and acetic acids. 

(b). Add a few drops of strong sodium 



PROTEINS 67 

hydroxide to a few cc. of the albumin solution. 
Repeat the test with strong potassium hydroxide. 

(e). Prepare four test-tubes each con- 
taining about 4c c. of the egg albumin solution. 
To the first add a solution of mercuric chloride, drop by 
drop, until an excess of the reagent has been added. Note 
the changes which occur. Repeat the experiment with 
lead acetate solution, silver nitrate solution and a solu- 
tion of copper sulphate. 

(d). To 5cc. of the albumin solution add 
picric acid, drop by drop until an excess of 
the reagent has been added. Repeat the experiment with 
^a solution of tannic acid. 

(e). Add a few drops of alcohol to 5cc. of the 
albumin solution. What is the effect? 

3. — Color Reactions. 

(a). Biuret Reaction. — To 5cc. of the albumin 
solution in a test-tube add an equal volume of sodium 
hydroxide and then add a drop or two of very dilute 
copper sulphate solution. A violet color appears. 

(b). Millon's Reaction. — Add a few drops of 
Millon's reagent* to 5cc. of the albumin solution in a test- 
tube. A precipitate appears which turns reddish on boil- 
ing. 

(c). Xanthoproteic Reaction. — To 5cc. of the 
albumin solution add an equal volume of concentrated 
nitric acid. Heat until a yellow precipitate or solution is 
obtained. Cool thoroughly and then neutralize with con- 
centrated ammonium hydroxide solution. The color 
changes to orange which is the Xanthoproteic reaction. 

4. Salting Out Experiments, (a). — To 25cc. of 5 
per cent egg albumin solution in a beaker add solid pow- 

^Millon's reagent is made by dissolving mercury in 
its own weight of concentrated nitric acid; then adding 
to the solution twice its volume of water. After standing 
for a short time the clear liquid is decanted off and used 
as the reagent. 



68 PROTEINS • 

dered ammonmm sulphate to the point of saturation. 
Keep in the water-bath at about 35° for half an hour. 
Filter, test the filtrate by the biuret test and the precipi- 
tate by Millon's test. When making the biuret test in 
the presence of ammonium sulphate or magnesium sul- 
phate it is necessary to add an excess of sodium hy- 
droxide, preferably a solid stick. Does the filtrate con- 
tain protein? What are your conclusions? 

(b). Repeat the above experiment making the 
saturation with solid sodium chloride. How does the re- 
sult difi'er from the result of the saturation with am- 
monium sulphate? All proteins are precipitated from 
their solutions by saturation with ammonium sulphate 
with the exception of the peptones.. Globulins are the 
only proteins precipitated by saturation with salt. Can 
you explain why the water solution of white of egg con- 
tains globulins as well as albumins? Are globulins sol- 
uble in pure water? 

5. Acid- Albuminate.— To 25cc. of egg albumin solu- 
tion add 2cc. of 0.2 per cent hydrochloric acid and heat 
on the water-bath at 40° for a few minutes. Acid al- 
bumin is formed. 

(a). To 5cc. of the solution of acid albumin 
add a few drops of litmus. The solution becomes red. 
Now add dilute sodium hydroxide until the solution just 
changes to blue. The acid albumin is precipitated. It 
redissolves on the addition of an excess of the alkali. 

(b). Heat a portion of the acid albumin solu- 
tion to boiling. Is a precipitate formed? 

6. Alkali-Albuminate. — To 25cc. of albumin solu- 
tion add 5c c. of sodium hydroxide and heat gently for a 
few minutes. Alkali-albuminate is formed whenever al- 
bumins or globulins are treated with alkalies. 

(a). Add a few drops of litmus to 5cc. of the 
alkali-albumin solution and just neutralize with dilute 
hydrochloric acid. What is the precipitate? 

(b). Heat a portion of the alkali-albumin solu- 
tion to boiling and note presence or absence of a pre- 
cipitate. 



PROTEINS 69 

II. Tests With Proteins of Milk. 

Mix 25cc. of milk with 75cc. of water, warm to 37°, 
and add dilute acetic acid, drop by drop, stirring, until 
the casein separates out as a flaky precipitate. Filter and 
use the precipitate for the tests. Test a portion of the 
filtrate with biuret and Millon tests. 

1. — Test the solubility of the precipitated casein 
in dilute acids, dilute alkalies, and in water. 

2.— Make the biuret and Millon tests with por- 
tions of the casein (Solution. 

III. Proteoses and Peptones. 

Dissolve 20g. of commercial peptone in lOOcc. of 
water. Warm in order to obtain a complete solution. 

1. — Put 5cc. of the solution in a test-tube and 
heat to boiling. Is there any coagulation? 

2. — Make the biuret test with about 5cc. of the 
solution. What is the color? 

3. — To 50cc. of the solution add 50ce. of a satur- 
ated ammonium sulphate solution. Stir well. The pre- 
cipitate consists of the primary albumoses. Filter. 
To the filtrate add two drops of sulphuric acid and then 
add solid ammonium sulphate until the solution is satura- 
ted. Notice the sticky precipitate that adheres to the 
stirring rod and to the sides of the beaker. The preci- 
pitate consists of the secondary albumoses. Filter; trans- 
fer some of the precipitate to a test-tube, dissolve in a 
little water and make the biuret test. Test a portion 
of the filtrate for peptone by adding an excess of solid 
sodium hydroxide and then making the biuret test. 
Which class of proteins are not precipitated by satura- 
tion with ammonium sulphate? 

IV. Gelatin. 

1. — Test the solubility of some commercial gelatine 
in cold and hot water, in 0.5 per cent sodium carbonate 
solution, in 2 per cent hydrochloric acid, in alcohol, in 
concentrated hydrochloric acid and in concentrated po- 
tassium hydroxide solution. 



70 



PROTEINS 



2. — Hydrate Ig. of gelatin with 5cc. of cold water and 
dissolve by adding 45cc. of boiling water. With portions 
of this solution make the following tests: 

(a) Precipitation. Test with concentrated sul- 
phuric acid, with alcohol, tannic acid, and mercuric 
chloride. 

(b) Color tests. Make biuret, Millon's, and 
Xanthoproteic tests. 

Questions. 

1. — Name some of the most common protein foods. 
Which proteins ocoiir most frequently in our foods? 

2. — What is the composition of proteins? 

3. — At what temperature should eggs be cooked? 
— ' 4. — Why is white of egg given in cases of lead or 
mercury poisoning? 

5. — What would be the eifect of strong tea on a solu- 
tion of proteins ? Tea contains a considerable amount of 
tannin. 

6.— Why does milk curdle when it sours? 

Tabulate the Results of the Protein Experiments Accord- 
ing to Following Table: 



PROTEIN HEAT 



PRECIPITANTS 



coagula- 
tion 



Albumin 

Globulin 

Casein 

Proteoses 

Peptones 

Gelatin 



dkalies 



salts of 'alkaloidal 
heavy reagents 
metals ; 



COLOR REACTIONS 



NaCl or 
(NH4)2 biuret 
SO4 



Millon 



Xantho- 
proteic 



PROTEINS 71 

Experiment No. 25. — Tests for nutrients in foods 

Eeading. — Sherman, pp. 41-44. 

Snyder, pp. 1-27. 
With the following foods make tests according to the 
general scheme* given below : 

(a) Bean soup. 

(b) Bouillon. 

(c) Milk, or commercial ice cream, or any other li- 
quid food. 

Scheme for the detection of the more common nutrients. 
1. — Preliminary tests. 

(a) Test reaction with litmus paper. 

(b) Make Xanthoproteic or biuret tests for proteins. 
If proteins are present proceed with tests given under 2. 
If no proteins are indicated proceed with the tests given 
under 3. 

2. — Test for proteins. 

(a) Albuminates. If the original solution is 
acid or alkaline : neutralize with dilute sodium carbon- 
ate, if acid, or with very dilute sulphuric acid if alkaline. 
A precipitate in either case indicates the presence of an 
acid or alkali-albuminate. If the original solution is 
neutral there are no albuminates in the solution. 

(b) Albumins and globulins. If the original 
solution is neutral, acidulate with a few drops of dilute 
acetic acid and boil. A precipitate indicates albumins or 
globulins. Filter and keep the filtrate for (c). If no pre- 
cipitate is obtained proceed at once to (c). If a precipi- 
tate is obtained saturate some of the original solution 
with salt. A precipitate indicates globulin. 

(c) Add to some of the original solution, or to 
the filtrate from (b), its own volume of saturated am- 
monium sulphate solution. A precipitate indicates pri- 
mary proteoses. Filter. 

(d) Saturate the filter from (c) with solid am- 

^Stewart, Manual of Physiology, pp. 4-10. 



72 



PROTEINS 



monium sulphate. A precipitate indicates the secondary 
proteoses. Filter. 

(e) Add a stick of solid sodium hydroxide to the 
filtrate from (d) and make the biuret test. A positive 
reaction indicates peptones. 

3. — Test for carbohydrates. 

If original solution is opalescent starch or glycogen 
are indicated. 

If original solution contains proteins acidulate with 
dilute acetic acid and boil, then filter. Use filtrate for 
tests. « 

(a) Starch, glycogen or dextrin. To a few cc. of 
the solution add a drop of iodine solution. If solution is 
alkaline neutralize before adding the iodine solution. A 
blue color indicates the presence of starch. A reddish 
brown color indicates dextrin or glycogen. Glycogen 
gives an opalescent solution while dextrin does not. 

(b) Reducing sugar. Make Fehling's test with 
a portion of the solution. 

(c) Cane-sugar. If tests (a) and (b) are nega- 
tive boil 20cc. of the solution with Ice. of concentrated 
hydrochloric acid for a few minutes : neutralize and 
make Fehling's test. A positive test indicates that cane 
sugar is present in the original solution. 

Tabulate your results as follows: 



FOOD 


PROTEINS 




CARBOHYDRATE 




albumin 

or 
globulin 


proteose 


peptone 


starch 


dextrin 


glycogen 


Sugar 




reducing 
sugar 


cane 
sugar 













































CHAPTER XVI 

Baking Powders 

Baking Powders. The value of a baking powder is 
determined by the amount of available carbon dioxide 
which it yields and by the character of the residue 
left in the bread. The first factor is largely influen- 
ced by the age of the powder. Even if baking powders 
are kept closely covered there is considerable loss of car- 
bon dioxide on. standing. The character of the residue 
depends upon the kind of powder used. Baking powders 
consist of soda, (sodium bi-carbonate), and an acid salt, 
mixed with a certain amount of air-dried starch. The 
starch is hygroscopic and prevents the other substances 
from becoming moist. The powders are named according 
to the acid ingredient which they contain. The principal 
powders are cream of tartar, acid phosphate, and alum 
powders. The alum powders generally contain some 
other acid ingredient besides the alum. Alum baking 
powders are quite generally condemned. The employ- 
ment of alum in the preparation of any food is consider- 
ed an adulteration. 

The chemical reaction of baking powders is a reac- 
tion between the soda and the acid constituent and re- 
sults in the formation of a sodium salt of the acid and 
water and carbon dioxide. The salt formed in each case 
is left as a residue in the bread. The residue from the 
different powders is shown by the following reactions : 

Cream of Tartar Powder 

potassium bi- sodium bi- potassium 

tartrate carbonate sodium tartrate 
(cream of tartar) (soda) (Rochelle salts) 

KHC.H.Oe + NaHCOg ^^KNaC,H,06+ CO^+H^O 



74 



BAKING POWDERS 



calcmm 
acid phosphate 



Phosphate Powder 
soda calcium sodium 
tri hydrogen 
phosphate 



CaH^fPOJ^ + NaHC03 ->CaNaH3(POj2+C02+H20 



Alum Powders 
potash alum soda potassium 

sulphate 
Al3Ko(SOj4.24H20H-6NaH ( 03-^ICSO, 
aluminum hydroxide carbon dioxide 
+ 3 A1(0H)3 + 6C0, -f- 



+ 



sodium 
sulphate 
SNa.SO^ 
water 
24H2O 



The residues from the cream of tartar and phosphate 
powders are substances used as drugs. Both Rochelle 
salts and calcium sodium acid phosphate are con- 
sidered harmless when taken in the small amounts 
used in leavening agents. The aluminum hydroxide form- 
ed as a residue in alum powders is regarded as decidedly 
deleterious. The continued use of alum powders is said to 
impair digestion and result in gastric disorders. * 

Experiment No. 26. — Baking Powders 

Reading. — Leach pp. 332-346. 
Snyder, pp. 186-193. 

Apparatus. 5 beakers, 5 evaporating dishes, flask, 10 
test-tubes, water-bath, burner, Knorr or Geissler Ap- 
paratus for CO2. 

Material. Royal, Rumford, Calumet, K. C, and Unrival- 
led Baking Powders, dilute hydrochloric acid, bar- 
ium chloride solution, dilute nitric acid, ammonium 
molybdato solution, tmcture of logwood, ammonium 
carbonate solution, ammoniacal silver nitrate solu- 
tion, lime water, resorcin, concentrated sulphuric 
acid. 



*Jago — Technology of bread making, p. 467. 



BAiaNG POWDERS 75 

Tests. 

1. — starch. — Place two grams of the baking powder 
in a beaker and add lOOce. of water. Heat to boiling and 
observe the thickness of the starch paste. Make this test 
with all the powders and compare the different powders 
in regard to the relative amount of starch which they 
contain. 

Mix 5 grams of the baking powder with lOOcc. of 
distilled water in a flask. Shake well and allow the starch 
to settle out. Decant the liquid through a filter. Use 
this solution for the tests given below. 

2. — Sulphates. — To about 5cc. of the baking powder 
solution add a few drops of dilute hydrochloric acid and 
then add Ice. of barium chloride solution. The formation 
of a white precipitate, (barium sulphate), indicates the 
presence of sulphates. 

3. — Phosphates. — Add a few drops of nitric acid to 
5cc. of the baking powder solution and then add 5cc. of 
ammonium molybdate. The formation of a fine yellow 
precipitate, especially on warming, indicates the presence 
of phosphates. 

4. — Tartrates. — If the baking powder contains phos- 
phates make test (a) for tartrates, otherwise test accord- 
ing to (b). 

(a). Applicable in the presence of phosphates. 

Evaporate 25cc. of the solution to dryness on the 
water-bath. Transfer the residue to a test-tube, add an 
equal amount of dry resorcin, and then a few drops of 
concentrated sulphuric acid. Heat gently. A rose-red 
color indicates the presence of tartrates. 

(b). To 5cc. of the baking powder solution add 
2cc. of ammoniacal silver nitrate and warm gently. The 
formation of a silver mirror on the sides and bottom of 
the test-tube indicates the presence of tartrates. 

5. — Alum. — Mix 2 grams of baking powder with 5cc. 
of water in an evaporating dish ; add a few drops of tinc- 
ture of logwood and 2cc. of ammonium carbonate solu- 
tion. Heat over water-bath and observe color. A blue 



76 BAKING POWDERS 

color indicates alum but a lavender or pink color shows 
pretty definitely that there is no alum present. 

6. — Available carbon dioxide gas. — Determine the 
amount of available carbon dioxide gas in a sample of the 
baking powder according to the official methods of the 
Department of Agriculture, Bui. No. 107, Bur. of Chem., 
pp. 169-175, or. Leach pp. 336-8. 
Questions. 

1. — Compare prices of pure tartrate and pure 
phosphate baking powders. Why should an alum pow- 
der not be used? 

2. — Would ft be practical to prepare your own bak- 
ing powder for use in the home ? 

The formulas below have been worked out for the 
preparation of baking powders. Obtain prices of the ma- 
terials and calculate the amount which could be saved by 
preparing the powders at home. 

Cream of tartar powder Phosphate powder 

cream of tartar lib. acidphosphateoflime l%lb. 

baking soda V2lb. baking soda . . „ lib. 

corn starch V2lt)- corn starch lib. 

3. — A baking powder is judged by the amount of 
available carbon dioxide gas which it yields and by the 
nature of the residue which it leaves in the bread. If a 
phosphate and a cream of tartar powder yield the same 
amount of available carbon dioxide which would you con- 
sider best to use ? 



CHAPTER XVII 
Food Adulterants 

Foods are adulterated chiefly by the use of substitu- 
ted products, and by the addition of coloring matter and 
preservatives. 

Food Substitutions. When food materials have been 
replaced by some inferior or imitation product, the con- 
sumer is forced to pay for a direct fraud. Many of the 
low grade flavoring extracts and so-called cheap teas and 
coffees consist wholly, or in large part of substituted ma- 
terials. All substances sold in bulk give the producer a 
good opportunity for sophistications. Ground spices, 
mustards, and peppers are frequently badly adulterated. 
The house-wife may learn to recognize adulterations in 
this class of products by buying the whole berries and 
comparing with the suspected articles. It is well to 
avoid substances sold in bulk not only for economical but 
for sanitary reasons also. 

In .some instances food substances command such a 
high market price that many consumers are forced to use 
a substituted food. If the substituted food is pure and 
wholesome and is sold as a substitution, there can be no 
objection to its use. The use of such foods should be en- 
couraged rather than restricted. The use of substituted 
vegetable fats in place of the more expensive animal fats 
is an indication of the desire on the part of the consumer 
to secure a wholesome product at lower cost. The only 
danger connected with the sale of butter and lard substi- 
tutes is that some unscruplous dealer may sell the artifi- 
cial for the real article. There are some simple tests, 
however, which enable the housewife to distinguish be- 
tween the food and its substitution. 

Coloring Matter. The addition of coloring matter to 
foods may enhance their esthetic appearance but general- 
ly such addition serves merely to disguise an inferior ar- 



78 FOOD ADULTERANTS 

• 

tide. By the use of coloring matter manufacturers of 
food products are able to palm off on the unsuspecting 
public inferior, damaged, or substituted materials. Ex- 
cellent? strawberry preserves are made out of glu- 
cose, saccharine- timothy seeds, apple pulp, artificial 
strawberry flavor, and coloring matter. Without the use 
of the coloring matter it would be impossible to deceive 
the consumer. Inferior vinegars are colored to represent 
the best grade of cider vinegars. Raspberry and other 
fruit jellies are prepared without a particle of the fruit 
in them. Tomato refuse is mixed with some cheap pulp, 
spices are added and then the mixture is colored and put 
on the market as tomato catsup made from "fresh ripe 
tomatoes ' '. 

The Pure Foods Laws require the use of coloring 
matter in food products to be stated on the label under 
which the food is sold. Thus the consumer, if he reads 
the label, will know he is buying a dyed product. 

In testing for coloring matter in foods, it is neces- 
sary to distinguish between the artificial coloring matter 
which has been added to the food, and the natural color- 
ing matter which would be present in the food from 
fruits or vegetables used in its manufacture. Artificial 
colors are generally prepared from coal tar products and 
are called coal tar dyes. 

Preservatives. The preservatives most commonly 
used in foods are formaldehyde, borax and boric acid, 
sulphites, salicylic acid and sodium salicylate, and ben- 
zoic acid and sodium benzoate. Preservatives have much 
the same effect as coloring matter. By their use dam- 
aged, inferior, and spoiled products may be foisted on the 
public. The addition of a small amount of sodium sul- 
phite to tainted meat restores the fresh red color of the 
meat and wholly disguises all odors of putridity. If the 
consumer is deprived of the two ways by which he judges 
freshness of food products, namely- appearance and odor, 
he will have little to guide him in the selection of food. 



FOOD ADULTERANTS 79 

Experiment No. 27. — Tests for some common adulterants 

in foods 

I. Tests for Formaldehyde in Milk or Cream. 

Leach p. 180. 

Apparatus. Test-tube, thistle-tube, porcelain casserole 

burner. 
Material. Milk or cream, concentrated sulphuric acid, 

concentrated hydrochloric acid (commercial, sp. gr. 

1.2,). 10 per cent ferric chloride. 

Hehner's Test. — Place 5cc. of milk in a test-tube and 
add 3cc. of concentrated sulphuric acid through a 
thistle tube in such a way as to form a distinct layer 
in the bottom of tlie tube. The formation of a violet 
or blue ring at the junction of the two liquids indi- 
cates the presence of formaldehyde. 

Hydrochloric Acid Test. — Place lOcc. of milk in a por- 
celain casserole and add an equal volume of concen- 
trated hydrochloric acid to which has been added 
one drop of 10 per cent ferric chloride. Heat slowly 
over a small flame for a few moments, giving the cas- 
serole a rotary movement to break up the curd. Do 
not allow the liquid to boil. The presence of for- 
maldehyde is indicated by a violet coloration. This 
is a very delicate test as it serves to indicate as small 
an amount of formaldehyde as one part in 250,000 
parts of milk. 

II. Tests for Oleomargarine and Process Butter. 
Apparatus. Table spoon, burner, splint of wood, beaker, 

pan. 
Material. Butter, oleomargarine, process or renovated 

butter, milk. 
*' Spoon Test. "..Farmers' Bui. 131,— Place a lump of 
the sample in a table spoon and heat over a small flame, 
stirring constantly. Pure butter boils quietly and foams 
a great deal. Oleomargarine sputters noisily and foams 
scare elv at all. 



80 FOOD ADULTERANTS 

t 

Waterhouse Test. 

Farmers' Bui. No. 131. — Heat 50cc. of sweet milk in 
a beaker and when near boiling add 5 grams of the fat. 
Stir with a small splint until the fat is melted. Place beak- 
er in a pan of ice water and continue stirring until the 
fat solidifies. At this point, if the sample is oleomargarine, 
the fat can be collected in one lump at the end of the 
stirrer. Butter can not be so collected but will remain 
in a granular condition distributed through the milk. 

In the ''Spoon" test the sample if process butter will 
behave like oleomargarine, i. e., will not foam. In the 
Waterhouse test process butter behaves like true butter, 
that is, it can not be collected by the stirrer. 

III. Test for Cotton Seed Oil in Compound Lard, Olive 
OIL etc. 

Leach p. 518. 
Apparatus. Beaker, test-tube, ring-stand, burner. 
Material. Lard, olive oil, Halphen's reagent, (equal 
volumes of amyl alcohol and carbon bisulphide, the 
latter containing 1 per cent of free sulphur), saturat- 
ed salt solution, cotton wool, cotton seed oil. 
Halphen Test. 

Mix 5c c. of the sample with an equal volume of Hal- 
phen's reagent in a test-tube; stopper the test-tube loose- 
ly with cotton wool, and suspend in a beaker of boiling 
saturated salt solution. (Precaution! Care must be tak- 
en to prevent the mixture in the test-tube from catching 
on fire. Do not use a high flame. Have test-tube suspend- 
ed in an upright position.) Keep t'he test-tube in the boil- 
ing solution for 15 minutes. If the oil darkens, i. e., 
shows a red or orange coloration, the presence of cotton 
seed oil is indicated. Make a control test with cotton 
seed oil. 

IV. Test for Coal-Tar Colors in Ketchup, or Jelly, Jam 
or Candy. 

Leach pp. 907, 794. 
Apparatus. 4 beakers, ring-stand, burner. 
Material. Sample of ketchup or whatever substance is 



FOOD ADULTERANTS 81 

to be tested, 10 per cent hydrochloric acid, strips of 
pure white woolen cloth, 1 per cent hydrochloric 
acid, 1 per cent sodium hydroxide, 2 per cent am- 
monium hydroxide. 

Method of Sostegni and Carpentieri, Zts. anal. Chem., 
1896, 35:397. 

Dissolve about 20 grams of the sample in lOOcc. of 
water, filter into a beaker and add 3cc. of 10 per cent hy- 
drochloric acid. Prepare some strips of fat free woolen 
cloth by washing strips of pure white wool in a 1 per cent 
solution of sodium hydroxide and then washing well in 
water to remove the alkali. Immerse a strip of this 
cloth in the acid solution in the beaker and boil over a 
low flame for 10 minutes. Remove the cloth to another 
beaker, cover with 1 per cent hydrochloric acid and boil. 
Pour off the acid, wash well with water, cover with a 2 
per cent solution of ammonium hydroxide and boil again. 
As soon as the ammonia solution has taken up the color 
well, remove the cloth and immerse a second strip of fat 
free wool in the ammonia solution. Acidify the solution 
w^ith a little dilute hydrochloric acid and boil for a few 
minutes. Examine the second strip of wool carefully. If 
it is colored, coal-tar dyes are indicated. Vegetable and 
fruit colors give no color to the wool in this second dye- 
ing. 

V. Test for Copper Salts in Canned Peas, Beans, or in 
Pickles 

Leach pp. 897-899. 
Apparatus. Large evaporating dish (250cc.), ring- 
stand, burner. 
Material. Can of peas or other ma^terial, concentrated 
sulphuric acid, concentrated nitric acid, concentrat- 
ed ammonium hydroxide. 

Evaporate the contents of the can to dryness in a 
large evaporating dish; add to the dry residue lOcc. of 
concentrated sulphuric acid and heat gently over a low 
flame until foaming ceases. Then burn the residue to an 



82 FOOD ADULTERANTS 

• 

ash in a hot flame. Moisten the ash with a few drops of 
concentrated nitric acid, add 50cc. of water- transfer to 
a beaker and boil; cool, make strongly alkaline 
with ammonium hydroxide and filter. If the filtrate is 
colored blue it is an indication that copper salts are 
present. 

VI. Test for Saccharin in Candies, Jellies, Jams, 
Syrups or Canned Products. 

Leach, pp. 842-843. 

Apparatus. Beaker, separatory funnel, evaporating dish, 

water-bath, test-tube. 
Material. Sample to be tested, phosphoric acid, ether, 

resorcin, concentrated sulphuric acid concentrated 

sodium hydroxide. 

Bornstein's Test. 

Macerate 50 grams of the sample in a mortar, dis- 
solve in water, and strain through muslin. If filtrate is 
not already acid, acidify with a few drops of phosphoric 
acid. Extract w4th ether in a separatory funnel. 
Evaporate the ethereal extract to dryness over hot water. 
Avoid flame! Mix the residue in the evaporating dish 
with an equal amount of dry resorcin and transfer to a 
test-tube. Add a few drops of concentrated sulphuric 
acid and heat until the mixture swells up; remove from 
flame and after the action ceases, heat again; repeat the 
heating and cooling several times. Finally cool, dilute 
with water and neutralize with sodium hydroxide. If 
saccharine is present the solution will show a red-green 
fluorescence. 

VII. Test for Starch and Gelatin in Jellies, Jams, 
Strained Honey, etc. 

Leach, pp. 922, 914, 915. 

Apparatus. 2 beakers, 2 test-tubes, ring-stand' burner. 

Material. Jelly, dilute sulphuric acid, potassium per- 
manganate, iodine solution, alcohol, tannic acid solu- 
tion, quicklime, hydrochloric acid, muslin cloth. 



FOOD Adulterants 83 

Detection of Starch. — Mix 25 grams of the sample 
with 50cc. of water, stir well, and strain through muslin. 
Heat the filtrate to boiling, remove from flame and de- 
colorize by the addition of dilute sulphuric acid and 
potassium permanganate. Filter some of the clarified 
solution into a test-tube, cool and test for starch by the 
a(klition of a drop of iodine solution. 

Detection of Gelatine. Make an aipieous extract of 
25 grams of the sample, strain through muslin, and add 
to the filtrate sufficient istrong alcohol to precipitate the 
gelatine. Divide the precipitate into two parts. Dis- 
solve one part in Avater in a test-tube and add a few drops 
of tannic acid. A precipitate indicates gelatine. 

Transfer the remainder of the precipitate to a test- 
tube and add a small lump of quicklime. Heat and test 
the vapors for ammonia gas. Te.st odor, reaction to 
moist litmus, and reaction to hydrochloric acid fumes. 
If gelatine is present ammonia Avill be given off by treat- 
ment with the ({uicklime. 

VIII. Tests for Chicory and Cereals in Coffee. 

Ltach, pp. 386, 388, 389. 
Snyder, pp. 203-214. 
Apparatus. Hand lens, 2 small flasks. 
Material. Pure roasted coffee beans, low grade coffee, 

saturated salt solution, chicory. 

Pure Coffee, (a). Obtain some properly roasted 
coffee beans of the best grade of coffee. Make a physical 
examination and also examine with a hand lens. 

(b). Grind up one gram of the pure sample in 
a mortar; transfer to a small flask and add 25cc. of sat- 
urated salt solution. Shake well and then examine. The 
lifiuid should be amber colored anci nearly all the mater- 
ial should float upon the surface. 

Chicory. — Repeat the tests given above with a sam- 
ple of low grade cott'ee. Chicory is more soluble than 
coffee and is also heavier. A cold water extract of coffee 
which contains chicory will show more color than will 
pure coffee. In test (b) the formation of much of a sedi- 



84 FOOD ADULTERANTS 

meiit indicates the presence of chicory. Make tests (a) 
and (b) with pure chicory. Compare the taste of chicory 
with that of coffee. 

Cereals. — Examine the low grade coffee with the 
hand lens for the detection of cereals. Roasted cereals 
show a polished surface which is very different from that 
of the roasted coffee bean. 

IX. Tests for Adulterants in Tea. 

Leach, pp. 374, 376, 378. 

Apparatus. Casserole, flask, (500cc.), sieve, beaker, 

liand lens or microscope. 
Material. Samples of high and low grade tea. 

Steins and Foreign Leaves.— Boil a gram of tea with 
200cc. of Avater in a casserole for 20 minutes. Pour off 
the water and examine the leaves. Make this test with 
tea which is known to be pure and with samples of low 
grade varieties. The presence of stems, dust, and foreign 
leaves can be detected in this way. 

Facing. — Mix two grams of tea with 500cc. of water 
in a flask. Shake well and strain through a sieve. Allow 
the insoluble materials remaining in the water to settle, 
tlien fllter and examine the sediment for mineral matter. 
The mineral pigments can readily be seen when the sedi- 
ment is examined under the microscope. 

X. Tests for Adulterants in Vanilla Extracts. 

Leach, pp. 849-855. 

Apparatus. Evaporating dish, water-bath, separatory 
funnel, 2 test-tubes, burner. 

Material. High and low grade vanilla extracts, 10 per- 
cent ammonium hydroxide, chloroform, iodine solu- 
tion, (2g. of crystallized potassum iodide dissolved 
in lOOcc. of water and .saturated with, iodine). 

Test for Coumarin (Extract of Tonka Bean.). 

Leach, p. 859. 
Leach's Test. — Place 35cc. of the extract in an 
evaporating dish and heat on the water-bath until the al- 



FOOD ADULTERANTS 85 

coliol is driven off. Dissolve the residue in lOcc. of 10 
per cent ammonium hydroxide and extract with three 
portions of chloroform in a separatory funnel. Evaporate 
the chloroform extract to dryness on the water-bath ; add 
5cc. of water to the residue and warm gently. Filter into 
a test-tube, cool and add a few drops of iodine solution. 
If coumarin is present a brown precipitate will form and 
on stirring this will gather in dark green flakes leaving 
a clear brown solution. 

Compare samples of pure vanilla extract \/ich ex- 
tract of tonka. Note the difference in odor and taste. 

Artificial Vanilla — Add a few drops of lead acetate 
to 5cc. of the sample in a test-tube. The absence of a 
precipitate indicates the artificial product. An extract of 
the vanilla bean under these conditions forms a copious' 
white precipitate which soon settles to the bottom of the 
test-tube. A faint cloudiness should not be mistaken for 
a precipitate. . i ' 

XI. Test for Oil of Lemon in Lemon Extracts. 

Leach, 862, 863, 864. 
Oil of Lemon. — To one cc. of the extract in a test- 
tube add lOcc. of water. The amount of cloudiness indi- 
cates the amount of oil of lemon present. If no cloudiness 
results the oil is absent. Compare samples of low and 
high grade extracts in this respect. 



BIBLIOGRAPHY 

Slierinaii, Cheinistry of Food and Nutrition. New York, 
1906/'- 

Snyder, Human Foods. New York, 1908.* 

Leach, Food Inspection and Analysis. New York, 1909.* 

Snyder, Chemistry of Phmt and Animal Life. New York, 
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Richter, Organic Chemistry. Phil., 1905. 

Mann, Chemistry of the Proteins, London, 1906. 

Howell, Text-Book of Physiology, Phil., 1910. 

Stewart, Manual of Physiology, Phil, 1905. 

Hammarsten, A Text-Book of Physiological Chemistry, 
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Hawk, Practical Physiological Chemistry. Phil., 1909. 

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Wel)ster and Koch, A Laboratory Manual in Physiologi- 
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Rockwood, A Laboratory Manual in Physiological Chem- 
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Blyth, Foods, their Composition and Analysis, New York, 
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Halliburton, A text book of Physiological Chemistry, 
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Jago, Technology of Bread Making. Am. Edition, Chica- 
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Salkowski, A Laboratory Manual of Physiological and 
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New York, 1904. 



BIBLIOGRAPHY 87 

Simon, A Text-Book of Physiological (/lieinistry, New 
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Thorpe, Outlines of Industrial Chemistry, New York, 
1907. 

Sadtler, Industrial Organic Chemistry, Phil, 1908. 

Knight, Food and its Functions, London, 1895. 

Green, The Soluble Ferments and Fermentation, Cam- 
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Goldthwaite, Principles of Jelly Making, Bui, Dept. of 
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Bulletin of the Office of Experiment Station, U. S. Dept. 
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